How to Keep Your Phone Number Abroad With an eSIM
The worry that comes up most with first-time eSIM buyers isn't about coverage or price. It's “if I switch to this, will my bank still text me?” It will. A travel eSIM doesn't replace your number, it sits next to it. What matters is a handful of settings, and getting one of them wrong is how people end up with a roaming bill anyway.
What a travel eSIM does, and what it leaves alone
Think of the two lines as doing different jobs. Your home SIM is your identity: it's the number your bank, your doctor, your friends and your two-factor apps know. The travel eSIM is a pipe. It has no number you'd ever give anyone; all it does is give your phone cheap local internet.
That split is the whole trick. Everything that runs over the internet, meaning maps, WhatsApp, iMessage, FaceTime, email, ride-hailing, streaming, goes through the travel eSIM. Everything that's tied to your number on the old-fashioned network, meaning ordinary SMS and carrier calls, keeps arriving on the home line, as long as you leave that line switched on.
That's fine too. Plenty of people on a two-week trip just switch the home line off and rely on WhatsApp. But if there's any chance a bank, airline or work login will want a text code, keep the line on. It costs you nothing while data roaming is off.
The setup, step by step
| Setting | Home line | Travel eSIM |
|---|---|---|
| Line turned on | On | On |
| Cellular / mobile data | Not selected | Selected |
| Data roaming | Off | On (needed for the plan to work abroad) |
| Calls and SMS default | Your usual default | Not used |
On an iPhone that's Settings, Cellular, then Cellular Data, where you pick the travel line, and the per-line settings underneath for data roaming. On most Android phones it's Settings, Network & internet, SIMs, then “Mobile data” and the roaming toggle on each line. Menu names shift between Samsung, Pixel and others, but the three things to find are always the same: which line handles data, whether each line is on, and roaming per line.
Do this at home, over Wi-Fi, the evening before you fly. Installing the eSIM is covered in the install guide; the setup here is the ten seconds afterwards. Label the two lines something obvious like “Home” and “Travel” while you're in there, because at 1am in an arrivals hall you will not remember which one is Line 2.
Bank codes, 2FA and other texts
Incoming SMS reaches you through your home carrier, so the codes keep coming as long as the line is on and allowed to roam. What people trip over is the assumption that “roaming off” means “the line is off.” It doesn't. Data roaming is one switch, the line itself is another, and the Home row in the table above wants the line on with data roaming off.
- Does your home plan allow international roaming at all? Some cheap or prepaid plans block it, and then no text will reach you abroad. A quick call to your carrier settles this.
- Do incoming texts cost anything abroad on your plan? Many plans include them, some don't. Know which before a bank sends you four codes in a row.
- Can you move your important logins to an authenticator app? A code from an app works with no signal to your home carrier at all, and it's the one change that removes the whole worry.
Some carriers also support SMS over Wi-Fi calling, which lets texts arrive over whatever internet you're on, travel eSIM data included. It's worth switching on if your carrier offers it, though support varies a lot between carriers and countries, so treat it as a bonus and not the plan.
WhatsApp, iMessage and the apps tied to your number
WhatsApp, Signal and Telegram identify you by your number but don't care which SIM is delivering the data. So messages, voice notes and video calls just run over the travel eSIM. Nothing to reconfigure, and your chats stay exactly where they were.
The one thing to avoid is re-registering. If you reinstall WhatsApp, get a new phone, or log out while abroad, it wants to text a verification code to your number, and that only works if the home line is on and reachable. Do those chores before you leave, or after you're back.
iMessage and FaceTime work the same way, over data. A small gotcha: if iMessage shows a “waiting for activation” message after you switch lines, toggling it off and on again with the travel eSIM as your data line usually clears it.
When you actually do need a local number
Siima's eSIMs are data-only. For the vast majority of trips that's enough, because calls happen over WhatsApp and the rest of your life is on the internet anyway. But there are honest exceptions: a delivery driver who phones the number on your booking, a local bank or e-wallet that verifies with a domestic SMS, a long stay where landlords and clinics expect a local mobile. For those, buy a local prepaid SIM (or a plan that includes a number) on arrival, and keep the travel eSIM for data if it's better value. The eSIM vs SIM card guide walks through where each one wins.