Choose the travel eSIM for mobile data
After installation, open your SIM or cellular settings and select the travel eSIM as the line used for mobile data. The menu name differs by phone, but the principle is the same.
Be careful with data switching
Some phones can automatically switch mobile data to another SIM when the selected line has weak service. If your priority is avoiding home-carrier roaming data, review that setting before travel.
Roaming can be ON for the travel eSIM and OFF for the home SIM
Many travel eSIMs use roaming agreements to connect to a local partner network, so the travel eSIM may require data roaming to be enabled. That does not mean you must enable data roaming for your normal SIM.
Calls and texts are separate from mobile data
Keeping the home SIM enabled can be useful for receiving your usual number, but carrier charges for calls, SMS or voicemail can still depend on your home plan. Check those rules with your carrier.
Install the eSIM, label both lines clearly, disable unwanted data switching, and take a screenshot of the correct SIM settings so you can restore them quickly after landing.