here are the steps:

first get your MSL code from Sprint technical support, or using a seem editor at seem 55 (the only 6 digits that show up).

* enter ##786# to go to the RTN menu
* go to Reset
* enter your MSL code and say Yes (This will erase just about EVERYTHING important on the phone
* once the phone has reset, enter ###
* Choose Edit
* for the MDN / Mobile number, enter your number
* for the MSID, if you have not changed carriers, enter your phone number again (i'm not too sure if this is correct for everyone. it worked for me, though)
* select Done and the phone reboots.

sounddoc