The the P2 (P200) and P3 (P300) can be reprogrammed by means of a cable which attaches to your computer's parallel port and the phone's accessory connector. All the software below requires this cable. NAM programming is done through test mode. Several programs below can put the phone into this mode.
P3 PROM, modified to allow ESN change from the keypad. Unknown if this will work on the P2.
Note: using the programs below may require you to translate ESN formats.