Last updated: September 20, 2026
You keep your regular SIM from your carrier at home, head overseas, and add a travel eSIM for data on the ground. Then you land, and it's not clear which line your data is actually running on—we hear this from travelers all the time. This guide walks through how to keep your home-country SIM in place for your phone number while making the travel eSIM your primary data line, with separate steps for iPhone and Android. The short version: you only need to do two things—set the travel eSIM as the line used for mobile data, and turn data roaming off on your home-country SIM.
- How to set the travel eSIM as your mobile data line
- Why data roaming should be off on your home-country SIM
- On iPhone, also turn off "Allow Cellular Data Switching"
- How your number and SMS stay with your home-country SIM
- The three settings to check if data isn't switching over
The "which line am I on?" problem after landing
In most cases, the confusion with a dual-SIM phone comes down to one thing: you haven't explicitly told the phone which line to use for mobile data. Simply adding a travel eSIM doesn't guarantee your phone will pick it for data automatically.
When you keep your home-country SIM and add a travel eSIM, your phone now has two lines side by side:
- Your home-country SIM: the line tied to your regular phone number. Keep it, but with the expectation that it won't carry data while you're abroad.
- Your travel eSIM: the line dedicated to local data. Maps, social media, translation, and app-based calls all run on this one.
If this division of roles isn't reflected in your settings, you can end up with situations like "I added the travel eSIM but my data was still going through my home SIM," or the reverse, "I turned off data roaming on my home SIM and now nothing connects at all." Both are almost always fixed by reviewing the settings, so take it step by step.
Before you switch: did you finish your pre-departure checks?
A smooth switch after landing depends on preparation before you leave. Specifically, that means two things: reviewing your home carrier's settings for overseas use (how data roaming is handled, whether your plan works abroad at all), and adding the travel eSIM to your phone ahead of time.
We've put together the pre-departure checklist in Taking Your Home-Country SIM Abroad: Pre-Departure Roaming Settings Checklist. If you haven't left yet, work through that first, then come back to the post-arrival steps in this article—it'll save you a lot of guesswork.
Keep in mind that whether your home carrier supports voice, SMS, and data abroad—and what it charges—can vary by plan and change over time. This article focuses on the settings on your phone itself. For your carrier's current overseas terms, check their official website.
iPhone: making the travel eSIM your primary data line
On iPhone, it's three steps: set "Cellular Data" to the travel eSIM, turn off "Allow Cellular Data Switching," and turn off data roaming on your home-country SIM.
1. Set the travel eSIM as the line for cellular data
Go to Settings → Cellular → Cellular Data, and you'll see a screen where you choose which line handles data. Select your travel eSIM here. Lines are shown by the label you gave them when you added them (e.g., "Travel" or "Secondary"), so giving your eSIM a clear name in advance makes this step easier.
2. Turn off "Allow Cellular Data Switching"
On the same Cellular Data screen, you'll find "Allow Cellular Data Switching." When this is on, your iPhone may automatically route data through your other line (your home-country SIM) if the travel eSIM's signal is weak. To avoid unintentionally roaming on your home SIM, it's safest to leave this off while abroad.
3. Turn off data roaming on your home-country SIM
Go to Settings → Cellular, tap your home-country SIM's line name, and turn off "Data Roaming." Data roaming is set per line, so the standard setup is: travel eSIM configured according to your plan's instructions, home-country SIM set to off.
4. You can leave your home-country SIM line turned on
"Turn On This Line" can stay on for your home-country SIM. With the line on but data roaming off, data flows through the travel eSIM while your phone number stays on your home SIM. Whether you can receive calls or SMS abroad depends on your home carrier's overseas support, so if that matters to you, confirm with them before you leave.
Android: making the travel eSIM your primary data line
The idea on Android is the same as on iPhone: set the travel eSIM as the SIM used for mobile data, and turn off data roaming on your home-country SIM. Menu names and locations vary by manufacturer and OS version, though, so treat the steps below as a typical flow.
1. Choose the preferred SIM for mobile data in SIM settings
On most Android phones, go to Settings → Network & internet → SIMs (or "SIM cards & mobile networks"). You'll see details for each line and options to choose which SIM is preferred for calls, SMS, and mobile data. Set the preferred SIM for mobile data to your travel eSIM.
2. Turn off data roaming on your home-country SIM
Open your home-country SIM from the SIM list and turn off "Roaming" or "Data roaming." Configure the travel eSIM according to your plan's instructions.
3. Watch for differences between device brands
On Galaxy phones it's under Connections → SIM manager; on other devices it may sit under Network & internet. The entry point differs. Typing "SIM," "Dual SIM," or "Preferred SIM" into the search bar in Settings is usually the fastest way to find it. Your device manufacturer's official help pages are the most reliable source for specifics.
Quick reference: settings for home-country SIM × travel eSIM
Here's the standard configuration while you're abroad. If you get lost after landing, compare this table against your phone's settings.
| Setting | Home-country SIM (for your number) | Travel eSIM (for data) |
|---|---|---|
| Line on/off | On (keeps your number) | On |
| Line used for mobile data | Not selected | Select this one |
| Data roaming | Off | Follow your plan's instructions |
| Allow Cellular Data Switching (iPhone) | Off (prevents data from automatically falling back to your home-country SIM) | |
| Default line for voice calls and SMS | Home-country SIM | Not selected (data-only) |
Whether data roaming needs to be on for the travel eSIM depends on the plan. For Bloomy eSIM, follow the instructions sent to you after purchase. The general setup flow is covered on our setup page.
Who this setup is for—and who it isn't
Keeping your home-country SIM and adding a travel eSIM for data suits people who want to hold on to their regular phone number while buying only the local data they actually need. If you make and receive a lot of calls on a local number, though, you'll want to consider other options.
A good fit if you…
- Want to keep your home-country phone number active without cancelling, and use it as normal when you get back
- Mainly use maps, social media, translation, and messaging apps like WhatsApp while abroad
- Want to choose just the amount of data you need for your trip length
- Prefer to add the eSIM before departure so that all you do after landing is switch lines
Consider other options if you…
- Frequently need to make or receive calls or SMS verification codes on a local number (look into a local SIM or a plan that includes a number)
- Use a phone that doesn't support eSIM (check our list of eSIM-compatible devices first)
- Want something you can just insert and use without touching any settings (a physical SIM may suit you better)
Good to know: data-only eSIMs and your phone number
Travel data eSIMs, including Bloomy eSIM, are data-only and don't come with a phone number. That means the travel eSIM can't make or receive regular voice calls or send and receive SMS. App-based calls that run over data—WhatsApp, Messenger, FaceTime, and similar—work as usual. The simplest way to think about it: the only things you lose on the travel eSIM are calls and texts to a phone number.
Keeping your home-country SIM is exactly about letting it handle the phone-number side. That said, whether calls and SMS to that number reach you overseas—and what it costs if they do—depends on your home carrier's roaming terms. If you expect to receive SMS verification codes from your bank back home or other services while abroad, check your carrier's latest conditions before you leave and set up an alternative way to receive them if needed.
Also, the speed and reliability of a travel eSIM depend on the local network, your device, coverage area, and congestion. Even within the same country, the experience can differ between city centers and outlying areas, so give yourself extra time for anything important. Plans labeled as unlimited are also subject to a fair use policy—speeds may be managed during periods of very heavy use.
Three places to check if data won't switch over or connect
If you have no data after landing, or you're connected on the wrong line, check three things: the line used for mobile data, data roaming on the travel eSIM, and Airplane Mode.
1. Is the travel eSIM set as the line for mobile data?
This is the most common culprit. Confirm that "Cellular Data" on iPhone, or the preferred SIM for "Mobile data" on Android, isn't still set to your home-country SIM.
2. Is data roaming on the travel eSIM set as instructed?
It's easy to turn off data roaming on your home-country SIM and accidentally turn it off on the travel eSIM as well. If your plan's instructions say it needs to be on, switch it back on for the travel eSIM only.
3. Toggle Airplane Mode on and off to reconnect
If the settings are correct but you're still not getting a signal, turn Airplane Mode on for a few seconds and then off again. This forces your phone to search for the local network again. If that doesn't help, work through the step-by-step checks on our troubleshooting page.
If you're still stuck, or you have questions before buying, take a look at our FAQ as well—it's written to be easy to scan even when you're stressed and on the go.
Summary: after landing, focus only on selecting the line
To keep your home-country SIM while making the travel eSIM your primary data line, you only need to cover three things: (1) set the travel eSIM as the line for mobile data, (2) turn off data roaming on your home-country SIM, and (3) on iPhone, also turn off "Allow Cellular Data Switching." Your phone number stays on your home-country SIM and your data runs on the travel eSIM—it's just a matter of reflecting that split in your settings, and it takes a few minutes after you land.
If you haven't done your pre-departure prep yet, go through the pre-departure roaming settings checklist first so the switch on arrival is even quicker. If you haven't picked an eSIM for your destination yet, you can browse plans by country, data amount, and trip length on Bloomy eSIM's comparison page. Bloomy eSIM installs with a single tap on the setup link sent after purchase, so the easiest approach is to add it before you leave and then switch lines using the steps in this article once you arrive. Pricing is shown in USD—please confirm the current price at the time of purchase.
The steps in this article are based on typical iOS and Android screens as of September 2026. Menu names and locations may differ depending on your OS version and device. Your home carrier's overseas terms and charges may change, so check their official website for the latest information.
