The short answer
Choose and install travel data before departure, while keeping control of voice, text, roaming, and your primary number.
Step by step
Confirm that the phone is unlocked, supports eSIM, and can use the destination network bands.
Compare your carrier's roaming option with local and regional eSIMs by data amount, duration, hotspot, calling, and renewal terms.
Install the eSIM on Wi-Fi before travel, label both lines clearly, and save the activation instructions offline.
Set cellular data to the travel eSIM and disable data roaming on the home line unless the home plan explicitly includes it.
Test messaging and authentication access, then monitor usage and the eSIM expiration date during the trip.
Before you finish
Keep screenshots, receipts, chat transcripts, confirmation numbers, and the first bill after a change. Carrier terms and account eligibility can change, so verify the final price and conditions directly before submitting an order.