Originally Posted by DallasBill
You do not have to change anything!
If you are using GSM, all you have to do is buy a used COAM (customer owned and maintained) ATTWS phone from Ebay or get an unlocked one. You can then remove the SIM from both your sons' broken phones and put them in the new ones. Call ATTWS and tell them you need to activate these replacment COAM phones and you will need to give them the IMEI nums (phone ID).
If the phone is unlocked, you just have to switch the sim. You shouldnt have to call with any info. Its one of the big advantages of gsm over analog, digital, and pcs.