If you are trying to keep the character and you want to put it on your main account, The best option is to give teh scammed acc it's OWN Battle.net account, then wait 30 days, then if it has not been recalled in that time, transfer it to your main account and proceed to ban the scammed one. That is the only method I have found to ensure your main is safe and you don't lose anything.
EDIT:You have to wait 30 days before blizzard will allow you to transfer a character to another battle.net account for security reasons.