You can simply remove your SIM card... all your contacts are probably saved on that. And that way, you can re-insert it into your next phone.
The address book for BBs is saved on the phone, not the SIM card.
You can use Desktop Manager and the Back up and restore function to back up your device before sending it in. Also, if you click on advanced from back up and restore, you should be able to clear the address book database.
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