BB Bold :: Transferring Data Between Different Phones?

I recently upgraded from a Bold to a Bold 9900 and gave the old phone to my son, having first backed up all data, memos, addresses etc on the PC and erased everything from my old phone. When I restored my data on to my new phone a few days later it brought all his BBM chat contacts and messages (which he had loaded on to the Bold)on to my phone and wiped the corresponding entries from his phone.Clearly I copied and restored some ID wrongly, with the result that his BBM messages are being directed to my new phone.