| | Re: De-register phone
To add on to what Rambo said, if you intend to replace your old BB with a non-BB device, then you should call your carrier and ask them specifically to cancel your BIS account.
If you are replacing it with a new BB, then when you add your new IMEI and PIN to your BIS account, then the old one should be clear.
In any case, you need to wipe it to remove all the old data and apps.
Look at our FAQ for an article on Buying a BB from eBay. It is near the bottom of the list. That will give you an insight into some of the things that you need to look out for.