Identify the exact handset
Use the intended provider's compatibility checker, including the model or IMEI when requested. Check lock status with the original carrier. A phone can be unlocked and still lack supported voice, Wi-Fi-calling or 5G features for the destination service.
For a second-hand phone, verify legitimate ownership, return rights and whether it has unresolved restrictions. Avoid assuming that a successful Wi-Fi connection proves the cellular hardware is ready.
Keep the old service during preparation
Back up contacts and essential information. Make account recovery accessible if SMS delivery is interrupted during a port. Have trusted Wi-Fi available for eSIM activation or app installation.
A new SIM can be activated with a new number or used in a number-transfer process, depending on the provider. Confirm which path you are following. Do not cancel the old line to “release” the number before the receiving provider instructs the correct transfer.
Test actual features before closing the move
Verify calls both ways, SMS, voicemail and data without Wi-Fi. Check hotspot, Wi-Fi calling and any watch if they are important. Keep the old records until the final account is reconciled.
If data works but voice does not, investigate supported calling features and provisioning. If only one messaging app fails, review that app's number registration. Avoid a factory reset until the provider has checked the account and simpler causes.