Making the centro dial the correct voicemail number
When I ported my old number to my new Sprint account, everything worked except the voicemail was dialing the wrong number to fix it, Sprint support had me enter the dialpad and type ##248308 to enter the device activation screen.
On that screen my telephone number was incorrect. After changing it to the actual (ported) number the voicemail system worked perfectly. YMMV Warning: this may change your phone MSID and you may have to reactivate it.

