Check the phone settings for carrier lock or network lock status
Insert a SIM card from a different carrier and see if it works
Make a test call, send a text, or use mobile data with the different SIM
Look for a message saying the SIM is unsupported, invalid, or restricted
Contact the original carrier and ask if the phone is unlocked
Check the phone’s IMEI on the carrier’s unlock status page
Review the purchase receipt or account details for unlock confirmation
Use the phone’s IMEI with a trusted unlock status checker
Try activating the phone on another carrier’s network
If the phone was bought directly from the manufacturer, confirm whether it was sold unlocked