How to Turn Data Roaming On and Off

Data roaming is a per-line setting, not a phone-wide one. That matters, because the correct configuration when travelling with an eSIM is roaming on for the travel line and off for your home line — at the same time.

Get one of those backwards and you get the two classic outcomes: an eSIM that shows no connection, or a bill from your home carrier for data you thought the eSIM was carrying. Both are settings problems, not plan problems — the installation guide covers the rest of the first-run setup.

A travel eSIM is issued by a network you are not physically on. From that network’s point of view your phone is roaming, even though you are paying local rates and nothing extra will be charged. With roaming disabled the phone politely refuses to connect, which reads as "no service" and sends people back to the provider convinced the plan is broken. It is the first thing to rule out when mobile data will not work at all.

Your home SIM should stay switched on so calls and texts still reach you — that is the point of keeping it. But if its data roaming is left on, background app traffic can quietly use it at your carrier’s roaming rate while the eSIM you paid for sits idle.

Turning off data roaming for the home line does not stop calls or SMS. It stops only mobile data on that line, which is exactly what you want.

The path differs by platform, but the shape is the same: open the line, change roaming for that line, then choose which line carries data. On Android the toggle lives with the other per-SIM options, and Google describes it as letting the phone send data over other carriers’ networks — which is exactly what a travel eSIM needs it to do.

iPhone

1. 1Settings → Cellular.
2. 2Tap the line you want to change — each one has its own settings.
3. 3Cellular Data Options → Data Roaming, and set it per line.
4. 4Back on the Cellular screen, set Cellular Data to the travel line.

Android

1. 1Settings → Network & internet → SIMs.
2. 2Tap the SIM you want to change.
3. 3Toggle Roaming for that SIM.
4. 4Set Mobile data to the travel SIM.

Naming the lines when you install them makes this much less error-prone. "Japan" and "Home" are unambiguous at an airport gate; "SIM 1" and "SIM 2" are not.

• Calls and texts. They ride on the line whether or not data roaming is on.
• Wifi. Turning roaming off does not affect anything using a wifi connection.
• Charges from your own plan at home. Roaming applies only outside your carrier’s network, which is why the setting is safe to leave off permanently if you always travel with an eSIM.

The reason this setting matters at all is that a travel plan is usually cheaper than roaming on your home contract — often by an order of magnitude, and the three ways to avoid a roaming bill start with knowing what yours actually costs. One large exception, and it is worth knowing before you buy anything: if your line was issued in the EU and you are travelling within it, Roam Like at Home already gives you your domestic allowance at no extra cost, in all 27 member states plus Iceland, Liechtenstein, Norway, and — since 1 January 2026 — Ukraine and Moldova. The Commission has prolonged those rules until 2032, so this is not a temporary position to plan around. In that case leave your home data roaming on and buy nothing. Everywhere else, plans by destination, ranked on price per GB.