Tweet Phone Unlock Instructions for Blackberry 5xxx, 6xxx, 7xxx(Except for 7100):

Note: After phone is unlocked, remove the battery, insert SIM as
desired and re-insert the battery. Phone MUST be restarted to use
the new SIM card.
1) Power on
2) Go to Options.
3) Scroll to SIM CARD then press jog dial in once to select it
4) HOLD ALT (Half moon key on the lower left side) and press:
mepe (Please note that you will NOT see what you type on the
screen)
5) It will ask you for the unlock code. Enter it and then press jog
dial once to confirm and your phone is unlocked!