Simply put, Meglo, no, there isn’t anything further that can be done. As the Game Masters stated, they will investigate the reported scam (and have done so) and if verified they will take appropriate actions which will include removing any gains from the scamming character. Please understood though, direct support for WoW Classic is limited, as stated in the thread WoW Classic Customer Support and You.
I am sorry for the frustration this may have caused you and for the loss of those items. Hopefully you’ll be able to recover and get the helm you wanted.