The question we get most before people buy: "if I put a Tunisian eSIM on my phone, do I lose my UK number?" No. Your UK SIM stays exactly where it is, in the same phone, doing what it's always done — the eSIM just takes over the data so your network never gets the chance to charge you Rest of World rates for it. Here's exactly how the two work side by side, and how to set it up so nothing slips through.
Every eSIM-capable phone (iPhone XS or newer, most Galaxy S20+ and Pixel 3+ models) can run two SIMs at once — your existing physical UK SIM plus the eSIM we email you as a QR code. They're not a swap, they're a pair. Your UK SIM keeps its number, its contacts, its call and text service. The eSIM adds a second line that exists purely to carry data. You choose which line handles what, and for a Tunisia trip the setup is always the same: UK SIM for calls and texts, eSIM for data.
This is the same trick as buying a local SIM at the Tunis-Carthage arrivals counter, minus the passport registration form, the queue and the fiddly bit of removing your UK SIM and losing it in a hotel bin — the eSIM installs digitally, so the UK SIM never leaves the tray.
The whole method rests on one setting. Do this and your UK network physically cannot bill you for Tunisian data:
Do steps 3–5 on the transfer coach if you need to — it takes about a minute, and until you do, both lines just sit there with roaming off, costing nothing.
WhatsApp is tied to your UK number, not to a SIM. Once your phone has any working internet connection — which the eSIM provides — WhatsApp keeps sending and receiving on that same UK number exactly as it does at home. Group chats, voice notes, video calls to the grandparents, the message to the hotel about the airport pick-up: all of it rides over the eSIM's data for free, no roaming charge in sight.
iMessage and FaceTime work the same way on iPhone: they're linked to your Apple ID and phone number, not to which physical SIM is active. As long as the phone has data — from the eSIM — blue-bubble messages and FaceTime calls keep working. Android's RCS ("Chat features" in Google Messages) behaves identically, tied to the number and Google account rather than the active data SIM.
The one thing that changes: if a UK friend texts your number using plain SMS instead of WhatsApp or iMessage, that lands on your UK SIM as a normal text — see below for how that's handled.
Receiving a standard text on your UK number in Tunisia is free on all four major UK networks — it's sending, answering calls and data that rack up Rest of World charges, and you've switched data off. This matters for the two things people worry about mid-holiday:
If you want to make outgoing calls freely without watching a per-minute meter, WhatsApp Call, FaceTime Audio or Google Meet all route over the eSIM's data and reach any phone or the same apps on the other end, all attached to your normal UK identity.
A five-minute job, best done before you fly so you're not fiddling with settings in arrivals:
Will people know I'm not on my normal SIM? No — calls and texts still show your normal UK number to everyone you contact. Nothing about how you appear to others changes.
Can I still receive a delivery text or 2FA code? Yes, as long as it arrives as a standard SMS to your UK number — that keeps working with data roaming off.
What if my UK SIM has no signal at all in Tunisia? All four UK networks have Tunisian roaming partners, but some tariffs only connect for voice and text once a roaming pass or add-on is active — check with your own network before you fly. The eSIM setup still works for data either way; it's only the voice/text side that depends on your UK network's own arrangements.
Do I need to do anything when I land back in the UK? No — once you're back on UK soil your phone reconnects to the UK SIM as normal. You can leave the Tunisia eSIM installed (it doesn't renew or charge again) or delete it — either is fine. Its remaining balance is on the check my data page if you want to see what was left.
Does this work for a family with several phones? Yes — every phone does the same UK-SIM-for-calls, eSIM-for-data split independently, with its own eSIM. Our Tunisia guide covers sizing a plan per phone, and the plan finder does the arithmetic.
More on compatibility (which iPhones/Samsungs qualify, hotspot use, what happens if you run out of data) is in the FAQ.