If your device is locked, you can only use a SIM card/eSIM profile from your provider only.
Check Network-unlocked
- iPhone
Settings – General – About
If you can see “No SIM restrictions” on “Carrier Lock”, it’s not locked.
You need to contact your carrier and request “Unlock” if you have “SIM restricted”
- Android
1) Settings – Connections – Networks (Mobile Networks or Cellular Networks, etc.) – Select Network Operators
If multiple networks appear, your phone is likely unlocked.
2) Try SIM card from different carrier, and if it works, it’s not locked.
You need to contact your carrier and request “Unlock” if it’s locked.
You need to contact to your carrier (such as AT&T, Verizon, Orange, etc.) and request your device to be unlocked.