Originally Posted by John Clark
Ah....That's easy. Go to Options >Advanced Options >Service books. Delete all that say [Desktop]
But they need to delete your account too. Also, it might be a good idea to talk to them about pushing a new blank IT policy to your device to make sure that everything is enabled that they may have restricted while connected to their BES.
I'd just like to emphasize what he said. A family acquaintance of mine left his position, and kept his BB that he paid for, but had BES'd with the company. Long story short, a new IT guy apparently started, went through and remotely wiped or locked any handhelds he couldn't locate.
But, in any case, just send them an email and make sure they SEND A BLANK IT POLICY. Could cause you a lot of problems. :P