Your Blackberry has an "IT Policy" on it requiring the password. This policy needs to be removed.
Remove IT Policy - BlackBerryFAQ
Unlocking the BlackBerry so that it can be used on another carrier is completely different; you need to contact a commercial unlocker to get the code.
Click on "BlackBerry Unlock" at the top of this thread to use the unlocker associated with this forum.
Good luck.