Korean SIM or eSIM Activated but No Data or Texts? What to Check Before Deleting Your eSIM, Plus Each Carrier's Support for Foreigners

Korean carriers' eSIMs for foreigners are hard to fix the way you'd fix one from an overseas seller, by deleting it and installing it again. LG U+ states that once an eSIM has been installed on a device, it can't be reinstalled or reissued, and KT also says its eSIM can only be installed once and that it won't issue the QR code again if you delete it. SK Telecom lets you scan the QR code up to 10 times on the same device, but if you delete the profile while you're using it, you have to buy a new one no matter how many days are left. If you delete your eSIM first just because data won't connect, your plan can end right there.

The trouble spots are usually the same few. On a dual-line phone, data may be set to your home line, the data roaming switch may be set the opposite way from what your plan's instructions say, or your phone may be locked to your home carrier. Texts not arriving often isn't a fault either: you may not have done the passport check yet, or you may be on a data-only plan. But LG U+'s customer center (phone and messenger) and KT's foreign-language phone support are open only during weekday daytime hours, and we couldn't find SK Telecom's support hours on its site. If you land on a Friday night and get stuck, leave a message through a messenger app, and if you're at Incheon Airport, heading to a 24-hour counter is faster.

The steps and pricing for buying a SIM or eSIM at the airport are in our airport SIM and eSIM guide, and the postpaid lines you can get once you have your Alien Registration Card are covered separately in our phone activation and plans guide. The steps below are for when a line you've already bought isn't working.

How to Narrow Down the Cause From What's Shown on Screen

Before you fix anything, look at what appears in the status bar at the very top of your phone and on the Cellular (Mobile networks) screen in Settings. Where you need to make changes depends on what's shown.

If 'Out of service' is still there after you've turned the phone off and on several times, it's faster to move on to Step 3 than to keep fiddling with settings.

If you installed an eSIM in advance while abroad and can't see your phone number, that isn't a fault. LG U+ states that an eSIM's phone number isn't displayed outside Korea and only shows up after you enter Korea.

According to reports when it took effect, Korea introduced its unlocked-device policy (the blacklist system) on May 1, 2012, making it possible to activate service on a phone bought abroad with just a SIM, with no need to register its IMEI (the device's unique identification number). The 'IMEI registration' item in Apple's documentation applies only to certain countries.

Korean Carrier eSIMs Often Can't Be Reinstalled Once Deleted

If you follow the advice that's common in overseas sellers' eSIM guides, "if it doesn't work, delete it and install it again," with a Korean carrier's eSIM for foreigners, you could lose your plan. Here are the conditions the three carriers spell out.

In its plan notes, LG U+ says that if something goes wrong, you should not delete the eSIM and should contact its customer center (010-3998-1004) instead. None of Steps 1 to 4 below involve deleting your eSIM. On the reset screen in Step 4, don't pick any option that deletes an eSIM either.

SK Telecom also lists one refund exception. If you couldn't use the service because your phone is country-locked (carrier-locked) or doesn't support eSIM, you can request a refund. However, SK Telecom states that refunds aren't available once 30 days have passed since payment, so if you think your phone is the problem, ask its support channels right away, before deleting anything.

On an iPhone, the place to be especially careful is the reset screen. If you go to Settings > General > Transfer or Reset iPhone > Reset, you'll see 'Delete All eSIMs' as a separate item in the same list as 'Reset Network Settings'. According to the iPhone User Guide, tapping 'Delete All eSIMs' erases every eSIM stored on your iPhone, and to reconnect to a cellular network you'll have to set up a new eSIM or a physical SIM. The two sit close together, so read the full item name before you tap.

Step 1: Airplane Mode, a Restart, Then Check the Carrier Name

The first thing to do is get your phone to reconnect to the network. Of Apple's guidance for when 'No Service' or 'Searching' appears, here are the things worth trying first.

1. Turn on Airplane Mode for at least 15 seconds, then turn it off.
2. Turn your phone off and back on.
3. If there's an iOS update waiting, install it.
4. Connect to Wi-Fi, then go to Settings > General > About and see whether a carrier settings update pops up. Apple notes that when you insert a new SIM, you need to download the new carrier's settings.
5. If you're on dual SIM, check in Settings > Cellular that your Korean line isn't turned off, and if it is, tap 'Turn On This Line'.

The step at the end of Apple's guidance, "turn on data roaming when you're abroad," has a different answer for each plan, so we look at it separately in the Step 2 table.

On a Galaxy, Samsung Electronics' support documents say to first swipe down from the top of the screen and check that Mobile data is on. If that doesn't help, press the volume down key and the side key together to force a restart. Samsung Electronics notes that a forced restart leaves the data and files on your device as they are.

For a physical SIM, the order in KT's SIM user guide is a useful reference. Insert the SIM with the phone off, turn it on, turn off Wi-Fi and Airplane Mode, and turn on the data network. Then turn the phone off and on two or more times and check that the carrier name shows 'KT'.

After restarting, look at the carrier name at the top of the screen or in Settings. SK Telecom tells you to check that the carrier is set to 'SKT' or 'SKTelecom' before using its eSIM. For an eSIM from an overseas seller, check the seller's instructions for which name should show up when everything's working. Sellers like Airalo suggest choosing the network manually if your phone automatically latches onto the wrong one.

In April 2023, when travelers using Taiwanese roaming SIMs in Busan and Daegu posted on a Taiwanese forum (PTT) that their connection kept dropping, replies followed saying things got better after switching the iPhone's network selection to manual and picking a different Korean carrier's network. These are personal accounts, and they're about roaming eSIMs and roaming SIMs from overseas sellers. If you bought your SIM or eSIM from a Korean carrier, don't pick another company's network in manual selection, and if switching to manual doesn't help, set it back to 'Automatic'.

Step 2: Your Data Line Setting and the Data Roaming Switch

This is where people go wrong most often on dual-line phones with both their home line and a Korean eSIM turned on. Apple notes that an iPhone uses cellular data on only one line at a time. Even with a Korean eSIM installed, if data is set to your home line, you won't get internet through the Korean eSIM.

Here's the order LG U+'s site for foreigners gives for "when the internet doesn't work after installing an eSIM."

'Allow Cellular Data Switching' is a feature that lets your phone use cellular data from both plans depending on coverage and conditions (Apple). LG U+ says to keep it turned off. If it's on, your home line's data may get used depending on conditions (based on Apple's description).

Samsung Electronics' checklist includes these items too. Turn off Wi-Fi and see whether mobile data works, and check that you haven't gone over a data limit set on your phone under Settings > Connections > Data usage > Mobile data usage > Settings > Data limit. If only one particular app won't work on an iPhone, check that cellular data isn't turned off for that app. Apple notes that if an app's cellular data is turned off, the app uses Wi-Fi only.

For the data roaming switch, the right setting is the opposite depending on the plan. Even among Korean carriers' eSIMs for foreigners the guidance differs, and eSIMs from overseas sellers are different again.

So leave the roaming switch as your seller's installation instructions say, and if you turned it on, check that roaming on your home line hasn't been turned on along with it. Airalo says that on an iPhone you can turn roaming on separately for each SIM, but on Android, roaming usually applies to all the SIMs in use at once, so to avoid roaming charges you should turn off your home SIM. If the data roaming switch on a Galaxy is grayed out and won't toggle, Samsung Electronics says to first check that mobile data is on (Settings > Connections > Mobile networks > Data roaming).

On iPhones running iOS 26 or later, when you arrive abroad and the 'Turn On Travel eSIM' alert appears, you're asked to choose between 'Travel eSIM Only' and 'Travel eSIM and Current eSIM' (as shown on English-language screens). Apple notes that if you use both lines together, data goes through the travel eSIM, but roaming charges may be incurred on your home eSIM.

Many people keep their home line on so they can get bank verification texts from home. An iPhone uses data on only one line but can send and receive texts on both numbers (Apple), so set data to the Korean eSIM and turn off data roaming on your home line. Even so, as Apple's guidance above says, keeping your home line on can still incur roaming charges with data roaming off. There are plenty of posts from people who briefly turned on home-line roaming when their eSIM wouldn't connect and then worried about the bill, so before you keep your home line on, check your home carrier's roaming rates first (including charges for receiving calls and texts abroad).

Step 3: Carrier Locks and eSIM Support, Causes Settings Can't Fix

If the QR code scanned but you keep getting 'No Service', it's time to suspect the phone itself. All three carriers state that their plans for foreigners only work on phones whose country lock (carrier lock) has been removed. SK Telecom also points out separately that even if the QR code scans, the plan can't be used unless the phone is unlocked.

On an iPhone, if you see 'No SIM restrictions' next to 'Carrier Lock' under Settings > General > About, the phone is unlocked. On Android, the menu differs by model, so as SK Telecom advises, check with the manufacturer or the home carrier you're currently with.

A lock isn't something a Korean airport counter can fix. Apple says only the carrier you currently have a contract with can unlock an iPhone, and that it can take a few days. KT also says to check your unlock status through the carrier you currently use, and LG U+ recommends contacting your carrier and getting the phone unlocked before you come to Korea. If your phone is locked, ask your home carrier to unlock it, and until it's unlocked, you'll have to get online through airport or accommodation Wi-Fi, a pocket Wi-Fi, or your home carrier's roaming. How to choose between pocket Wi-Fi and roaming is in our pocket Wi-Fi, eSIM, SIM, and roaming comparison.

If your phone was bought in Japan, SIM locks have been prohibited in principle since October 1, 2021 under guidelines from Japan's Ministry of Internal Affairs and Communications. Japanese carrier devices released before then may be locked, but some have already been unlocked, so don't guess from the purchase date and check directly on the settings screen above.

Whether your phone supports eSIM is another thing to check. Dial *#06# on the phone app's keypad and your device information will appear, and LG U+ says that if you see an EID, you can use an eSIM. SK Telecom says that if 'eSIM IMEI' appears, or an EID starting with '89' appears, the phone can install an eSIM.

If your phone doesn't support eSIM, you'll need a physical SIM. How to get a SIM at an airport counter is in our airport SIM and eSIM guide.

If only one person's phone won't work among family members who bought the same eSIM, suspect that phone's lock status, eSIM support, and data line setting before buying another one.

Step 4: Check the APN and Network Mode, Then Reset Network Settings

If the carrier name shows up correctly but only data won't work, it's time to look at the APN (data connection settings). That said, editing APN values yourself is a last resort. Apple warns that entering the wrong APN can cut off your cellular data connection and lead to extra charges, and says not to edit it unless your carrier tells you to. If your carrier supports it, on iOS 16 and later the values are filled in automatically under Settings > Cellular > Cellular Data Network, and you can only view or edit them if your carrier allows it. Apple says values you've already changed can be put back to the defaults with 'Reset Settings'.

KT's SIM user guide says to check the APN if the carrier name shows 'KT' but data doesn't work, and gives the path Settings > More networks > Mobile networks > Access Point Names. If you've changed the values, follow Samsung Electronics Service's guidance to restore them: Settings > Connections > Mobile networks > Access Point Names > More (three dots) > 'Reset to default'. We couldn't confirm the APN values for the three carriers' plans for foreigners in official sources, so we haven't listed them here. If you need the values, ask the carrier or seller you bought from. Airalo notes that some eSIMs from overseas sellers require you to enter the APN manually.

Switching between 5G and LTE is another thing to try.

• iPhone: Choose LTE under Settings > Cellular > Cellular Data Options > Voice & Data to turn off 5G (iPhone 12 and later on a 5G plan).
• Galaxy: Choose from 5G/LTE/3G/2G (auto connect) under Settings > Connections > Mobile networks > 'Network mode'. Samsung Electronics suggests switching between the available modes and checking the connection each time.
• eSIMs from overseas sellers: Airalo also suggests switching from 5G to 4G/LTE.

If it still won't work, reset your network settings ('Reset Network Settings' on iPhone, 'Reset network settings' on Galaxy). This is also what LG U+ suggests trying before you contact its customer center when the internet won't connect.

On Android, the reset list differs by model. If you see an item or checkbox in the list that deletes eSIMs, don't select it, and reset only the network settings.

After resetting, check two things again. If your saved Wi-Fi networks were erased, you'll need to re-enter your accommodation's Wi-Fi password, and data roaming may have been turned off, so set it again to suit your plan using the Step 2 table. If you're on an overseas seller's eSIM that needs roaming turned on, this could be exactly why the internet isn't working after the reset. Don't tap 'Delete All eSIMs' in the iPhone reset list.

On a Galaxy, you can also run a mobile network diagnosis in the Samsung Members app > Support > Get Started > 'Mobile network' (per Samsung Electronics; menu names may differ by model and version).

If your laptop is connected to your phone's hotspot (tethering) and that's the only thing not working, try turning your phone off and on (per LG U+). How much tethering you can use differs by plan. Some plans, like SK Telecom's 5G plan, cap it at 1GB a day, so check the details of the plan you bought.

When the Internet Works but Texts and Calls Don't

If the internet works but texts or calls don't, look at the conditions of the plan you bought before your settings. Korean carriers' plans for foreigners are split into data-only plans and plans that include voice and texts, and even on a voice plan, texts sometimes don't open up until you've finished the passport check.

LG U+'s official FAQ table and its blog table say different things about whether its data-only plan can receive texts. If you need to receive verification texts, it's safer to follow LG U+'s advice and choose a data + voice plan from the start.

For SK Telecom's voice plans, you can verify your passport online with the email voucher once you've cleared arrival procedures (passed immigration), but online verification only works daily 8:00–22:00. Outside those hours, you show your physical passport at an airport roaming center to get verified. If you landed at 11 p.m. and are waiting for a verification text from a taxi app, it may not be arriving because your passport hasn't been verified yet.

Only verify through the QR code on the email voucher or contract SK Telecom sent you, or on the passport verification page of SK Telecom's roaming center site (skroaming.com). Don't open emails or texts asking you to enter your passport number at any other address. Here's how online verification works.

1. Enter the rental contract number and phone number from your email voucher.
2. Enter your surname, given name, passport number, date of birth, and nationality.
3. Once a confirmation text arrives, you're done.

If verification fails, SK Telecom says to remove any special characters and spaces from your name and enter it again. One passport can verify only one plan at a time, and foreigners staying 91 days or longer and passports issued in Korea can't use this verification. Even before passport verification, you can call SK Telecom's roaming customer center (02-6343-9000) and receive calls from it.

Even once you have a number, none of the three carriers' traveler plans can be used for bank or government identity verification. LG U+ says its voice plans do work for text verification when you sign up for restaurant or taxi booking apps, but SK Telecom states that personal verification services and payment-related texts can't be received, and KT also says KT SIMs don't support personal verification. What you can do without a Korean number is collected in our guide to what you can do without identity verification.

Sometimes a text does arrive but you can't see it. iOS 26's 'Screen Unknown Senders' is off by default, but if you had 'Filter Unknown Senders' turned on in iOS 18, it gets turned on when you upgrade to iOS 26. When it's on, texts from unknown numbers show up under the filter button > 'Unknown Senders' in the Messages app. According to Apple, urgent messages like verification codes still notify you by default, but they're moved to 'Unknown Senders' after appearing in the conversation list for 8 hours.

If you're on dual lines, also check that the number you're verifying matches the line receiving texts. There's a case of a Japanese traveler who had signed up for an app with their home number and then turned their home line off, so the notification came in but they couldn't see the message. Steps for checking each line one at a time are in the verification text checklist in our KakaoTalk sign-up guide.

For calls, it's normal for your other line to show 'No Service' while you're on a call. Apple notes that if Wi-Fi Calling isn't supported or isn't set up, your other line shows 'No Service' during a call. LG U+ and SK Telecom say incoming calls and texts are free, and SK Telecom says outgoing calls and texts work after you top up credit. Outgoing rates for LG U+ SIMs and eSIMs (plans that include voice) are ₩4.4 per second for calls within Korea (₩264 per minute), ₩55 per text within Korea, ₩1,100 per MMS, and ₩165 per international text (international call rates vary by country).

When It Suddenly Cuts Out After Working Fine: Check the Period, Allowance, and Bill

If it worked fine for a few days and then suddenly cut out, check your plan period before your settings. When the period starts counting differs by carrier.

If you install a KT eSIM before leaving home, the days start counting down from then, while LG U+ counts from when you first use data. Don't assume that "an eSIM's days don't count down until you arrive in Korea, even once it's installed" holds for all three carriers.

KT states that if your phone's data roaming is on when the eSIM's validity period ends, it automatically switches to data roaming and roaming charges apply. If you keep using it without realizing the period has ended, you may be running up roaming charges, so if the date has passed, check the roaming switch first.

Sometimes what feels like a "cutoff" is actually slower speeds after you've used up your daily allowance.

People staying a long time, like international students, sometimes get cut off while renewing travel plans back to back. SK Telecom's eSIM for foreigners is only for foreigners on short trips of 90 days or less, so service may be restricted if you stay 91 days or longer, and KT's plans can't go past 90 days in total, counting the rental period plus extensions from the day you first activate. Neither company accepts payment with credit or debit cards issued in Korea, so some people get blocked when they try to buy the same plan again after getting a Korean card. If you're staying a long time, you'll need to move to a resident line opened with your Alien Registration Card, and how to do that is in our phone activation and plans guide.

If you suddenly can't make calls on a postpaid resident line, check for unpaid bills too. Under carrier terms, continued non-payment can lead to service suspension, and you're supposed to be notified before that happens. This is based on news reports from 2021 on a Korea Communications Commission decision about LG U+'s terms, and we couldn't confirm the current wording in the three carriers' terms. Ask your carrier's customer center whether you have unpaid bills (for LG U+, 114, free for U+ customers).

If It Still Won't Work: Carrier Support for Foreigners and 24-Hour Airport Counters

If you've gone through all the steps above and it still won't work, ask the carrier or seller you bought from. Even without data, you can leave a message through a messenger app once you're on airport or accommodation Wi-Fi. If your eSIM came from an overseas seller (such as Airalo), start with that seller's customer support.

For messenger support, go in through the messenger icons and links or the live chat button on the customer center screen of the carrier's site for foreigners. Accounts that come up when you search by name in a messenger app are hard to tell apart from official ones, so if you have to search by ID, check character by character that it matches the ID listed on the site. If anyone asks for your card password or a verification code during a chat, stop the conversation.

Think about call charges too. LG U+'s 010-3998-1004 is free only when you call from a U+ phone, and charges apply otherwise. If you call on your home roaming line instead of the Korean line that isn't working, roaming call charges may apply, so if you want to ask for free, messenger or website chat is the better choice. KT's number is free from a KT phone, and SK Telecom's 02-6343-9000 works for calling and receiving calls even before passport verification. LG U+ says foreigners living in Korea can also ask at 114 (U+ customers, free) or 080-851-1004 (non-U+ customers, free). A 2022 news report said 080-851-1004 offered interpretation support in English, Chinese, and Vietnamese, but we couldn't confirm which languages it supports now. We also couldn't confirm foreign-language support numbers for SK Telecom and KT resident lines this time.

If you land on a Friday night or a weekend and phone support is closed, an airport counter is the alternative. At Incheon Airport, all three carriers have 24-hour counters in the 1st floor arrivals hall. At Gimpo and Gimhae, none of the three carriers has a 24-hour counter.

Bring your passport when you go to a counter. At night, SK Telecom's passport verification for voice plans is also done at an airport roaming center with your physical passport. How to get from the airport into the city late at night is covered in our Incheon Airport late-night arrival guide.

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Frequently Asked Questions (FAQ)

Q1. I installed an eSIM in Korea, but the internet doesn't work. What should I check first? A. Start by checking that your data line is set to the Korean eSIM. On an iPhone, pick the eSIM under Settings > Cellular > Cellular Data, and on Android, under Settings > Connections > SIM manager > Mobile data, and LG U+ says to keep 'Allow Cellular Data Switching' (on Android, 'Data switching') turned off. If that doesn't help, go through a restart, the roaming switch, the carrier lock, and a network settings reset, in that order, and finally ask the carrier you bought from.

Q2. I deleted my Korean carrier eSIM. Can I install it again? A. LG U+ and KT say you can't. LG U+ says an eSIM can't be reinstalled or reissued once it's been installed, and KT won't issue the QR code again once you delete it, so you'd have to buy a new one. SK Telecom lets you scan the QR up to 10 times on the same device within 180 days of purchase, but says that if you delete the profile while you're using it, you have to buy a new one no matter how many days are left. If you've already deleted it, start by explaining the situation to the support channels of the carrier you bought from.

Q3. Should data roaming be on or off when I use a Korean eSIM? A. It differs by plan, so the right move is to follow the installation instructions from wherever you bought it. KT recommends keeping it off for its eSIM for foreigners so roaming charges don't kick in after the period ends, while eSIMs from overseas sellers sometimes need it on. We couldn't find official wording on the roaming switch for LG U+ and SK Telecom eSIMs for foreigners. Either way, if data roaming on your home line gets turned on as well, your home carrier's roaming charges may apply, so check.

Q4. Verification texts aren't reaching my Korean SIM or eSIM number. Why? A. You may be on a data-only plan, or your passport may not be verified yet. SK Telecom voice plans can receive texts once your passport details are verified as genuine (online verification daily 8:00–22:00 after arrival procedures), and KT voice plans can send and receive texts once you've completed identity verification (entry verification). Verification is done at an airport roaming center, and the identity verification page on KT's roaming site also mentions online verification daily 8:00–22:00 after immigration (Vietnamese and Indonesian passport holders verify at an airport roaming center). None of the three carriers' traveler plans work for bank or government identity verification, and on an iPhone, also check whether the text has been moved into the 'Unknown Senders' filter in iOS 26.

Q5. Will resetting network settings delete my eSIM too? A. 'Reset Network Settings' on an iPhone doesn't delete your eSIM. This item erases network settings such as Wi-Fi and VPN, and 'Delete All eSIMs', the item that deletes eSIMs, sits separately in the same reset list (iPhone User Guide). That said, cellular data roaming may be turned off after a reset, so set it again to suit your plan, and read the full item names so you don't tap 'Delete All eSIMs' by mistake.