I believe it is the phones internal serial number (IEMI) which is hard coded into the hardware that is sometimes locked to a network.
If the phone is reported as stolen to the current airtime provider, then they can mark the IEMI on a central database preventing it from ever being used on any network again.
Mike
If the phone is reported as stolen to the current airtime provider, then they can mark the IEMI on a central database preventing it from ever being used on any network again.
Mike
