Short answer: turning off data roaming is necessary but not sufficient. Three things bill separately — data, voice, and SMS — and data roaming controls only the first. Change the settings below before you fly, choose your data path deliberately, and check the bill after you land, because roaming charges can arrive weeks later.
What to change before you fly
Do these in order. The first two take a minute and prevent almost every surprise charge.
1. Decide what the home line is allowed to do. Data roaming off is the minimum: Settings → Cellular → Cellular Data Options → Data Roaming. If you do not need to receive calls on your home number while abroad, turning the line off completely (Settings → Cellular → [your line]) is the only setting that guarantees no voice or SMS charges.
2. Set up your data path. Either a travel eSIM installed before departure, or a local SIM bought on arrival. Do not plan to rely on airport Wi-Fi for maps and messages — it is the most common way a first day abroad goes wrong.
3. Turn on Wi-Fi Calling if your carrier supports it. With it on, calls to your home country can route over Wi-Fi or over your data connection rather than the foreign network. It has to be enabled before you leave, because it usually cannot be activated while roaming.
4. Check whether your phone is carrier-locked. A locked phone will not accept another carrier's eSIM or SIM. Check Settings → General → About → Carrier Lock. If it says anything other than "No SIM restrictions", a travel eSIM will not work and you need to sort the lock out first.
Data, voice, and SMS bill separately
This is the part that catches people, and it is worth reading twice.
| What you do abroad | Does "data roaming off" stop the charge? |
|---|---|
| Using mobile data | Yes |
| Making a call | No |
| Receiving a call | No — incoming calls are billed on most carriers |
| Sending an SMS | No |
| Receiving an SMS | Usually no, but some carriers bill it |
| Voicemail being deposited | No, on some carriers |
So a phone in a pocket with data roaming off can still accumulate charges. The only setting that reliably prevents this is turning the line off, not just its data.
That distinction also decides the right setup: if you want to keep receiving verification codes and calls on your home number, leave the line on and accept that calls carry a cost; if you want zero risk, turn the line off and use your eSIM's data with a VoIP app for anything you need to say.
Travel eSIM or local SIM
| Travel eSIM | Local physical SIM | |
|---|---|---|
| Set up before you fly | Yes | No |
| Keeps your home number active | Yes | No — the tray is occupied |
| Needs a shop visit | No | Usually |
| Cost per GB | Higher | Lower |
| Local number for calls | Usually no (data-only) | Yes |
The practical rule: short trip, want to keep your number → eSIM. Longer stay, want a local number → local SIM. Most travel eSIMs are data-only, which is fine for maps, messaging apps, and email, but they cannot receive an SMS — so anything that texts you a verification code must go to the home line, which is another reason to keep that line on with data roaming disabled.
Note the tray detail: on models with a physical SIM slot, inserting a local SIM means removing your home SIM, and with it your home number. eSIM avoids that entirely.
Why "I turned roaming off" sometimes is not true
Three common ways the setting is not what you think it is:
- Airplane mode was off at some point. Switching airplane mode off for one call, or connecting to Wi-Fi on landing, re-registers the line. A single brief registration is enough for a call to arrive.
- The charge is old. Roaming items can appear on a bill weeks after the trip. Read the itemised date, not the bill date, before assuming the setting failed.
- Only data roaming was off. As the table above shows, that leaves voice and SMS billing normally.
If a charge looks wrong, ask the carrier for the itemised record with timestamps. "Roaming charge" without a time and a service type is not answerable; with them, it usually is.
When you land, and when you get home
On landing: confirm which line is carrying data (Settings → Cellular → Cellular Data), and check that the phone shows the network you expect. If the eSIM shows no service, see eSIM activation failed and No SIM or SOS only.
Before you fly home: if you used a travel eSIM, decide whether to keep it for a future trip or delete it. A dormant eSIM costs nothing but can quietly take over the data line if it is set as primary.
After landing home: turn data roaming back off (it is a roaming setting, and leaving it on costs nothing at home but is easy to forget), confirm your home line is the data line again, and read the next bill for items dated during the trip. Do not delete a travel eSIM until the final bill has arrived — the ICCID is the reference the carrier will ask for if you dispute a charge.