[mbote]

Here are the steps you need to follow: (taken from the Bell Mobility User guide)

On normal ideal screen, Tap Start, then Tap Phone Icon
in Phone Dialler enter # # followed by 6 digit OTSL or MSL # and press Talk
On activation Wizard highlight the "MDN" field and tap Menu and then tap Edit. Enter the mobile number into the MDN field.
Highlight the MSID field and tap Menu and then tap Edit. Enter the mobile number into the MSID field.
Once completed entering all the changes tap OK in the upper right. A window will pop up with "update the items?" Tap Yes and the device will power cycle and complete and save all changes

Basically, MSID and MDN are generally your phone number and setting them to invalid data might just do what you need: clear the correct info from your device

My 2 cents, hth

claudius