How to stop your home carrier charging you roaming while you use a Korea eSIM

A Korea eSIM takes your internet off your home plan, but your home line stays switched on, and anything that line carries is still billed by your home carrier. Data can slip back onto the home line through two kinds of switch, data roaming and automatic data switching, so turn both off for the home line. Calls, texts and a couple of fallbacks keep running on your home number at your carrier's roaming rates, and only your carrier can tell you what those are.

This post is based on Apple, Samsung and Google support pages and on Kedanto's FAQ and Korea page, all checked on 30 September 2026.

What can your home carrier still bill once a Korea eSIM carries your data?

Three things: data that ends up on your home line, calls and texts on your home number, and calls or messages that fall back from the internet to the mobile network. Kedanto's Korea eSIM is data only, with no phone number and no SMS, and the Korea page says calls and texts to your usual number still reach the SIM you already have. So your home line stays on for the whole trip, and your home carrier bills whatever it carries under its own roaming terms. Apple says the same on its page about travel eSIMs: if you choose to use both lines, "your travel eSIM will be used for data. You might still incur roaming fees from your home eSIM."

Which switch stops your home plan from carrying data in Korea?

Data roaming on the home line. Leave it off from the day you fly until you're home. Apple defines it as the setting that "permits internet access over a cellular data network in regions that are not covered by your carrier's network." Samsung UK's page on roaming (updated 5 June 2026) puts the cost side plainly: "Your provider may charge you extra for data roaming." With the switch off, the home line has no way to carry mobile internet traffic in Korea.

The Korea eSIM line needs the opposite. Its data roaming has to be on, or it won't connect at all, and mixing up which line gets which setting is the usual mistake. If the eSIM itself won't connect, see When your Korea eSIM is switched on but the internet isn't.

Can your phone move data onto the home line by itself?

It can, if an automatic data switching setting is on. iPhone, Galaxy and Pixel each have one, and each is worth turning off for the trip.

• iPhone: Allow Cellular Data Switching. Apple says to turn it on "if you want your iPhone to use cellular data from both plans, depending on coverage and availability," and that with it on, a voice-only number on a call "automatically switches to use voice and data." A footnote on the same page says this switching during calls won't work while you're using Data Roaming, and that additional fees might apply. Turning it off costs you one thing, in Apple's words: cellular data won't work while you're on a call on a number that isn't your cellular data number.
• Galaxy: Auto data switching. Samsung's Caribbean support page (last updated 20 November 2024) lists it under Settings › Connections › SIM card manager and says it sets "the device to use another SIM card for data services if the preferred SIM card cannot connect to the network." In Korea, the other SIM is your home one.
• Pixel: Automatic data switching on Pixel 8a and later, Data during calls on Pixel 8, Pixel 8 Pro and earlier. Both sit under Settings › Network & internet › SIMs. Google lists Automatic data switching as one of the requirements for taking calls on both SIMs at once. For the older models it notes that "during a phone call, all data goes through the SIM making the call," and gives Data during calls as the switch for using data during a call on a SIM not normally used for data.

With data roaming already off on the home line, these settings shouldn't find a roaming connection to use. Turning them off as well gives you two separate barriers instead of one, which helps if a setting gets reset after an update or you tap the wrong line. Where these screens appear during installation is shown in where the iPhone and Galaxy setup screens differ.

Does turning off data roaming also stop charges for calls and texts?

No. The data roaming switch covers internet access only. Calls and texts on your home number roam separately, at your carrier's rates. Samsung Japan's explainer on data roaming says you can make and receive calls with data roaming off, because calls run over voice roaming, which that switch doesn't touch, and it says the same of SMS. Apple's travel eSIM page, for its part, says that if you keep both lines on, "the capabilities on your primary line will continue to work."

Whether an incoming call or text in Korea costs you anything, and how much, depends on your home carrier and plan. We can't give one number for that, and we won't guess. These are the questions to put to them before you fly:

• What does it cost per minute to answer a call while I'm in Korea?
• Do incoming texts cost anything while I'm there?
• If I don't answer and the call goes to voicemail, is that billed as well?
• Does my plan charge a daily roaming fee automatically, and if so, does a call or a text start it, or only data?

Apple adds one related warning on its Dual SIM page: if you forward calls from one number to the other, check with your carrier whether additional fees apply.

If the answers make an always-on home line too expensive, the other choice on an iPhone is Travel eSIM Only. For that setup, Apple names only FaceTime and iMessage as carrying on over your home line, so ordinary calls and SMS to your number, including bank codes, are no longer part of the picture. That trade-off is weighed in Getting verification texts on your home number in Korea.

Is Wi-Fi Calling free on your home line in Korea?

That depends on your carrier, and it may not work abroad at all. Apple's iPhone User Guide says Wi-Fi calling "isn't available with all carriers or in all countries or regions." Apple's Dual SIM page tells you to check with your carrier for availability "and find out whether additional fees or data usage applies." Google's Phone app help says the same for Android phones: "You may incur additional charges for making calls over Wi-Fi."

Apple also describes a handover worth knowing about. If the Wi-Fi connection is lost during a call, the call switches automatically to your carrier's cellular network using VoLTE, if that's available and turned on. For your home line in Korea, that cellular network is a roaming one, so a call that starts on hotel Wi-Fi and follows you out onto the street can finish as a roaming call. Ask your carrier whether Wi-Fi Calling works from Korea, and how a call made that way is billed.

The switch is at Settings › Cellular › your home number › Wi-Fi Calling on iPhone, and at Settings › Network & internet › SIMs › your carrier SIM › Wi-Fi calling on Pixel. We didn't find a Samsung support page on Wi-Fi Calling abroad, so on a Galaxy, go by what your carrier tells you.

Can iMessage or FaceTime end up on your home carrier's bill?

Not while they run over the internet. The one thing to watch is iMessage falling back to an ordinary text. Apple says iMessage is sent over Wi-Fi or cellular data, and that an iPhone uses one cellular data network at a time. With the Korea eSIM chosen as your cellular data line, iMessage and FaceTime use its data or Wi-Fi. Apple's travel eSIM page describes exactly this setup: once you've picked the travel line for data, you can keep using FaceTime, iMessage and other apps on your home line.

The fallback is a setting called Send as Text Message, under Settings › Apps › Messages. Apple says it makes Messages "automatically try to send messages as an SMS when iMessage isn't available," and when you send a message as a text by hand, it warns: "Messaging rates may apply." A text sent from your home number in Korea is charged at whatever your carrier bills for texts sent abroad. If you'd rather a message wait for Wi-Fi than go out as a roaming text, turn Send as Text Message off until you're home.

In what order should you set this up on an iPhone?

Close the home line's data routes before you fly, and point your data at the Korea eSIM after you land. The menu names below are Apple's; on some iPhones, Cellular is called Mobile Data.

Before you fly, on Wi-Fi at home:

1. Home line data roaming off: Settings › Cellular, tap your home number, tap Cellular Data Options, and turn off Data Roaming.
2. Allow Cellular Data Switching off: Settings › Cellular › Cellular Data.
3. Wi-Fi Calling: Settings › Cellular › your home number › Wi-Fi Calling, set according to what your carrier said about Korea.
4. Send as Text Message: Settings › Apps › Messages, on or off as you decided above.

After you land in Korea:

5. Korea eSIM as the data line: Settings › Cellular › Cellular Data, then tap the Korea eSIM line.
6. Korea eSIM data roaming on: Settings › Cellular, tap the Korea eSIM line, tap Cellular Data Options, and turn on Data Roaming.

If iOS 26 shows a Turn On Travel eSIM notification after landing, Apple says choosing Travel eSIM and Current eSIM puts your data on the travel eSIM. Check steps 1, 5 and 6 anyway once it's done. Apple's note on that choice is the one quoted above: you might still incur roaming fees from your home eSIM.

In what order should you set this up on a Galaxy or Pixel?

The same order applies: home line first, before you fly, then the Korea eSIM after landing.

On a Galaxy, the wording is Samsung UK's and Samsung Caribbean's; some phones say SIM manager instead of SIM card manager.

1. Before you fly: Settings › Connections › SIM card manager, and turn off Auto data switching.
2. After landing: in SIM card manager, tap Mobile data and choose the Korea eSIM.
3. After landing: Settings › Connections › Mobile networks, and turn on Data Roaming. Samsung UK's page gives this as a single switch with no step for choosing a SIM, and the Korea eSIM needs it on. On a Galaxy, then, what keeps data off your home SIM is steps 1 and 2. If your Mobile networks screen does ask you to choose a SIM, leave roaming off for the home one.

On a Pixel, the wording is Pixel Phone Help's.

1. Before you fly: Settings › Network & internet › SIMs, choose your home SIM, and turn off Roaming.
2. Before you fly: on the same screen, turn off Automatic data switching (Pixel 8a and later) or Data during calls (Pixel 8, Pixel 8 Pro and earlier).
3. After landing: tap Mobile data and choose the Korea eSIM.
4. After landing: choose the Korea eSIM and turn on Roaming. Google describes Roaming as letting your phone "send data over other carriers' networks when you leave an area covered by your carrier's networks."

Here is how it plays out when a call to your home number comes in while you're standing on a Seoul subway platform. With everything above in place, the call reaches you on your home line and none of your data has moved onto your home plan. If you answer, expect your map to pause until you hang up: with data switching off, Apple says cellular data doesn't work during a call on the number that isn't your data line. Whether to answer at all comes down to the per-minute figure your carrier gave you before you left.