TracFones whether GSM, CDMA or IS-136 "TDMA" all have special unique firmware in the handset that debits the account rather than as in traditional prepaid where all the account debiting is done in the operator's billing system. This is why some older TracFones do not debit for incoming text messages while the newer models do. The only way you can use handsets that were for Net10 or TracFone outside of their systems is if you have them reflashed with generic non-Net10 or TracFone specific firmware. Even though TracFone has GSM in many places you cannot take a regular SIM and insert it into a TracFone even if the SIM "subsidy" lock is defeated. In other groups it has been discussed and some think that you cannot even use a Net10 or TracFone handset interchangeably even though they both use the same handset-based debiting/charging system.