Last updated: August 25, 2026 (information current as of August 2026)
Once you land, the questions start: "What happens to calls to my regular number?" and "Now that I've added a data-only eSIM, should I take my usual SIM out?" Here's the short answer: if your phone supports dual SIM, you can keep your home-country SIM active purely for your number (incoming calls) while handing all internet traffic over to the data-only eSIM. This guide walks through what to set up before you leave and what to switch on when you arrive, screen by screen, for both iPhone and Android.
- Your number stays on your home SIM while data runs on the eSIM
- Three things to do before departure
- Data roaming on your home SIM should normally stay off
- App-based calls work fine on a data-only plan
- What to check, in order, if nothing connects
The short version: one phone, number on your home SIM, data on the eSIM
If your device supports dual SIM (a physical SIM plus an eSIM, or two eSIMs), you can give each line its own job. Your home-country SIM stays on standby holding your phone number, while maps, search, social media and app calls all run through the data-only eSIM you bought for your destination.
The key idea isn't choosing one line over the other — it's assigning roles. Turn off data roaming on your home SIM and all your traffic goes through the eSIM instead. Your number stays alive, and your connectivity costs are covered by a plan built for where you're going.
Start by confirming your phone supports eSIM and dual SIM. You can check yours on the eSIM compatible devices page. If you bought your phone from a mobile operator, it's also worth checking whether it's carrier-locked, since a locked phone may not accept another network's line.
What each line can and can't do
Before touching any settings, it helps to see the division of labour at a glance.
| What you want to do | Your home-country SIM (has a number) | Data-only eSIM |
|---|---|---|
| Voice calls to and from your phone number | Depends on your operator's international roaming terms and charges | Not supported |
| SMS to and from your phone number | Depends on your plan | Not supported |
| Internet access (maps, search, social, browsing) | Possible, but watch how roaming data is billed | Yes — this is what it's built for |
| App calls: WhatsApp, Messenger, FaceTime and similar | Works as long as you have a connection | Yes, since these calls run over data |
| Tethering / hotspot | Depends on your plan | Varies by plan |
The most common misunderstanding is reading "data-only" as "no calling at all." In practice, app calls over data — WhatsApp, Messenger, FaceTime and the like — work exactly as usual. What you don't get is voice calling and SMS tied to a phone number. As long as the person on the other end uses the same app, voice and video calls feel no different from home.
If you'd like a fuller explanation of how data-only eSIMs work, reading What is a data-only eSIM? Calls and SMS explained simply first will make the settings below make more sense.
Three things to do before you leave
A little preparation at home saves a lot of fumbling at the airport. There are three things worth sorting out in advance.
1. Check device compatibility and carrier lock
Confirm that your phone supports eSIM, that it can keep two lines on standby at the same time, and that it isn't locked to a single operator. Without these, none of the steps that follow will work.
2. Choose a plan for your destination and install it from the setup link
Pick a plan based on where you're going, how much data you need and how long you'll be there. You can browse options by country and data amount on the eSIM comparison page. After purchase, a single tap on the setup link you receive walks you through adding the eSIM on-screen. There's nothing to scan, and if the link doesn't work for any reason, a QR code and manual entry are available as backups. Full instructions are in the setup guide.
Install it before you travel, somewhere with a stable connection. Note that when to activate the line (for example, switching it on only after you arrive) varies from plan to plan, so follow the instructions that come with your purchase.
3. Decide each line's role in advance
Data = eSIM. Voice (your number) = your home SIM. Data roaming on your home SIM = off. Set those three before departure and all you'll need to do on arrival is switch the line on. The next sections cover how, device by device.
Leaving data roaming switched on for your home SIM can trigger data usage you didn't intend. Roaming charges and how incoming calls are handled abroad depend entirely on your contract, so check with your mobile carrier at home before you travel.
Setting it up on iPhone
In short: set "Mobile Data" (or "Cellular Data") to the eSIM, set your default voice line to your home SIM, and turn data roaming off on the home SIM. That's it. The flow below is typical, though menu names and their order can differ between iOS versions.
Choose the line used for data
Open Settings → Mobile Data (Cellular) and you'll see the lines you've added. Under "Mobile Data," select the eSIM for your destination. If this is left on your home SIM, your phone will keep trying to use that line abroad — so don't skip it.
While you're there, turn off "Allow Mobile Data Switching." That prevents your phone from quietly falling back to your home SIM whenever the eSIM's signal dips.
Set the line used for voice calls
On the same screen, choose your home SIM as the "Default Voice Line" so calls continue to be handled by your usual number. Whether you can actually receive calls abroad, and what it costs, comes down to your operator's international roaming terms — worth confirming in advance if calls matter to you.
Turn off data roaming on your home SIM
Under Mobile Data, tap your home SIM and switch "Data Roaming" off. Now all traffic runs through the eSIM. Conversely, your travel eSIM may need data roaming turned on — follow whatever the plan's instructions say.
iMessage, FaceTime and app calls
For iMessage and FaceTime you can choose which address or number is used to send and receive. When SMS to your number isn't available, setting your Apple ID email address or an app as your main channel keeps conversations with family and travel companions flowing. WhatsApp and FaceTime calls run over the data-only eSIM without any extra setup.
Setting it up on Android
The principle is identical: assign "calls" and "data" to different SIMs. Wording varies by manufacturer and Android version, so look for the closest match.
Assign a role to each SIM
Open Settings → Network & internet → SIMs (or "SIM cards & mobile networks") and you'll find per-line settings. Set "Mobile data" to your travel eSIM and "Calls" to your home SIM. Some phones label these "Preferred SIM" or "Default SIM."
Sort out roaming and automatic switching
Select your home SIM and turn roaming off. If your phone has something like "Automatically switch mobile data," switch that off too, so you don't end up connected on the line you didn't intend. Some models also let you select a network manually if the phone struggles to find one on arrival.
After changing settings, toggling airplane mode on and off often forces the lines to reload. If that doesn't help, a simple restart is the next calm step.
Who this setup suits — and who it doesn't
It isn't the right answer for everyone. Honestly, it splits along these lines.
A good fit if you
- Want to stay reachable on your home-country number while you're away
- Are on a short trip or business travel and can't afford to go dark on your number for work or family
- Want to keep costs down with a destination plan while holding on to your number
- Mostly keep in touch through app calls like WhatsApp
Less of a fit (consider other options) if you
- Need a local phone number for restaurant bookings, ride-hailing or banking where you're going
- Regularly receive SMS sent to your phone number (whether you can receive them abroad, and at what cost, depends on your contract)
- Have a phone that doesn't support dual SIM
- Are staying long term, where having a local number simply makes daily life easier
If you're in the second group, look at a local SIM or a plan that includes a phone number as well. Requirements differ by country and operator, so check current information for your destination.
What to check, in order, if you can't get online
In most cases it's one of two things: the line isn't switched on, or the wrong line is selected for data. Work down this list calmly.
- Is airplane mode off?
- Is the eSIM line switched on (enabled)?
- Is your travel eSIM the line selected for mobile data?
- Is data roaming on the eSIM set the way the plan instructions describe?
- Is data roaming on your home SIM still off?
- Try toggling airplane mode on and off, or restart the phone
- If nothing changes, try selecting a network manually
Symptom-by-symptom fixes are collected on the troubleshooting page. Right after landing it can take a few minutes for the phone to latch onto a network, so waiting a little before you start troubleshooting is often the answer.
Data-only still leaves you plenty of ways to stay in touch
What a data-only eSIM can't do is voice calls and SMS tied to a phone number. Everything else — WhatsApp, Messenger, FaceTime and similar app calls — runs over data and works as usual. Before you go, check that the people you contact most are reachable on the same app; it removes a lot of anxiety once you're abroad.
And by keeping your home SIM for your number, incoming calls can still reach you, subject to your contract's terms. "Keep the number, move the data" is a combination that suits short trips and business travel particularly well.
Wrapping up: five minutes before you fly, one switch when you land
There isn't much to it. Confirm your device is compatible, pick a plan for your destination and tap the setup link once, then settle the roles: data = eSIM, voice = home SIM, home SIM roaming off. With that done, arriving means switching the line on and getting straight online.
If you already know where you're headed, the eSIM comparison page lets you search by country, data amount and number of days. For questions before you set up or buy, our FAQ is a good place to start.
Bloomy eSIMs are data-only: they do not include a phone number, SMS or voice calling, and all plans are subject to a fair usage policy. Speeds and coverage vary with the local network, your device and where you are. Plan details, pricing and terms may change, so check the current listing at the time of purchase. This article describes the general process as of August 2026; setting names differ between devices and OS versions. How incoming calls and roaming are handled abroad depends on your own operator's terms, so confirm the latest official guidance before you buy and before you travel.
