Open Settings
Tap General
Tap About
Find Carrier Lock or Network Provider Lock
If it says No SIM restrictions, the iPhone is unlocked
If it shows a carrier name or SIM locked, the iPhone is locked
Insert a SIM card from a different carrier
If the phone connects and makes calls or uses data, it is unlocked
If you get a SIM not supported or invalid SIM message, it is locked
Contact the original carrier and ask them to check the lock status
Check the carrier account or device purchase records for unlock status
Use Apple Support or the carrier’s IMEI check tool if available