Method to perform subsidy protection for TDMA mobile stations

The method of activating a mobile station used in a TDMA cellular network system to provide subsidy protection for a cellular operator, comprising the steps of:

• installing a subscriber identity module (SIM) in the mobile station, the SIM initially having an IMSI file storing first indicia uniquely identifying the cellular operator, with a mobile identity number (MIN) field of the IMSI initially being blank, the mobile station storing second indicia uniquely identifying the cellular operator;
• comparing the first indicia to the second indicia to determine if the SIM and the mobile station are valid for the cellular operator;
• and
• if the SIM and the mobile station are valid, then storing a mobile identity number in the IMSI file MIN field of the SIM.