From Repair Mobile
[edit]
How to Enter Unlock Codes on BlackBerry 6xxx 7xxx: ie 6230, 7100, 7290 etc.:
1. Select Options menu on BB.
2. Now you select SIM CARD menu. To be able to see this you have to type this on the keypad on
phone : (TEXT WILL NOT APPEAR ON THE SCREEN until you enter the unlock code)
3. Type 'MEPD' for all models except 7100 in which case in case use 'MEPPD'.
4. Usually you should see "active" NET lock. Now in order to disable this lock type 'MEP2' respectively More details [1] - thanks to cellphonerepair.org
