Most travel eSIMs, Num’s included, sell you data. You get an internet connection in the country you are visiting. You do not get a new phone number, and you are not asked to give up the one you have.
For the majority of travellers that is the right product, because almost everything people mean by “staying in touch” now travels over the internet rather than over a number. But the distinction is real, it is rarely spelled out on a pricing page, and there is one case where it genuinely bites.
The two kinds of eSIM you can buy
Apple draws this line clearly in its own guidance for travellers, and it is the cleanest way to think about it:
| Travel data eSIM | Local provider eSIM | |
|---|---|---|
| What you buy | A prepaid data plan from a worldwide provider | A plan from a network operator in that country |
| Phone number | Normally none — data only | Often includes a local number |
| Buy it before you fly | Yes | Sometimes; often in person on arrival |
| ID required | No | Possibly — a passport may be needed, depending on local rules |
| Suits | Trips of days or weeks | Longer stays, or needing a local number |
Num is the first column. If you need the second, buy from an operator in the country itself — that is not a sale we are trying to win, and pretending otherwise would waste your time.
What still works with data only
More than most people expect. Everything here needs an internet connection and nothing else:
- WhatsApp, Telegram, Signal, Messenger — calls and messages included
- iMessage and FaceTime, which Apple confirms keep working on your home line while you travel
- Maps, ride-hailing, translation, boarding passes, banking apps
- Email, and any service that verifies you through an app or email rather than a text
Your messaging accounts are tied to the number you registered with, not to whichever line is carrying data at the time. Putting a travel eSIM in your phone does not sign you out of WhatsApp or move you to a new account.
What data alone cannot do
Three things, and only the third is a real problem:
- Receive a call to a local number. You do not have one.
- Send a normal SMS from a local number. Same reason.
- Receive an SMS sent to a local number. This is the one that catches people — a local delivery service, ticket site or clinic that will only text a domestic number.
Note what is not on that list: codes from your own bank. Those go to your existing number and keep arriving normally, provided your home line is still switched on. Turning off data roaming on the home line does not stop texts reaching it — it stops that line using mobile data, which is precisely what you want.
Keeping your own number while you travel
This is the setup worth using, and it is the reason a data-only eSIM is rarely a limitation:
- Leave your home SIM in place and switched on, so calls and texts to your usual number still arrive.
- Turn data roaming off on that home line.
- Set the travel eSIM as your data line: Settings → Mobile Data → Mobile Data.
You keep one number, in one phone, and only the data moves. Apple warns that if you leave both lines fully active you may still incur roaming fees from the home line, so step two is not optional.
Common questions
Does a Num eSIM include a phone number?
No. Num sells prepaid data. The plan adds a data line to your phone; it does not give you a new number, and it does not take your existing one away.
Will WhatsApp still work?
Yes. WhatsApp is tied to the number you registered with, not to the SIM currently carrying your data. Once it is set up it runs over any internet connection, so a data-only eSIM is enough. The same is true of Telegram, Signal, Messenger, iMessage and FaceTime.
Can I still receive my bank's verification code?
Usually yes, and this is the part people get wrong. Those codes go to your existing number, so they keep arriving as long as your home line is still switched on. What a data-only eSIM cannot do is receive a code sent to a local number in the country you are visiting.
When do I actually need a local number?
Rarely as a tourist. It matters if a local service will only send a code to a domestic number, if you need to be reachable on a local number for a landlord, clinic or employer, or if you are staying long enough to open local accounts.
How do I get a local number if I need one?
Buy from a network provider in that country rather than a worldwide travel provider. Apple notes that many local provider plans come with a local phone number, and that depending on local rules you may be asked for identification such as a passport to complete the purchase.
Browse travel data plans by destination →
Device behaviour and the local-provider details here are from Apple’s guidance on using eSIM while travelling internationally, checked on 2026-08-21.