The phone setting that lets a line use a partner network abroad. Travel eSIMs need it on.
Data roaming allows a line to connect to a network that is not its home network. A travel eSIM always connects through partner networks, so roaming must be on for the travel line.
The risk is on the other line. If your home SIM is the data line and roaming is on, your carrier may charge roaming rates.
What to check
- Turn roaming on for the travel line only
- Set the travel eSIM as the mobile data line and leave the home line for calls and texts