Check the phone’s settings for carrier lock or network lock status
Insert a SIM card from a different carrier and see if it connects to the network
Make a call or use mobile data with the different carrier SIM
Check the original purchase receipt or carrier account for unlock status
Contact the carrier and ask if the IMEI is unlocked
Use the phone’s IMEI on the carrier’s unlock status checker if available
Look for “No SIM restrictions” on iPhone in Settings > General > About
Look for “Network unlocked” or similar wording in Android settings, if shown
Restart the phone after inserting a different SIM to see if it registers
Check for messages like “SIM not supported” or “Invalid SIM,” which may indicate it is locked