Check whether you can use a SIM card from a different carrier
Insert a different carrier’s SIM and see if it connects to cellular service
Look in your phone’s settings for carrier lock or SIM lock status
On iPhone, go to Settings > General > About and check Carrier Lock
On Android, check Settings for SIM status, network lock, or carrier lock information
Contact your current carrier and ask if the phone is unlocked
Use your phone’s IMEI on the carrier’s unlock status checker if available
Try making calls, sending texts, and using mobile data with another carrier’s SIM
If the phone works with multiple carriers, it is likely unlocked
If the phone shows a SIM not supported or network locked message, it is likely locked