2 things you can do.
1. File an unauthorized claim, saying your account was breached and an unauthorized payment was sent to that other person.
2. Recall your WoW, call Blizz and tell them your account info was stolen, keylogger, fake program, your choice, and deny anything related to you selling the account, since blizz has been suspending accounts for that.
3. Do both of those together, so you get the account back, and the money!