FNB of no help when needed! Whats the point if your bank cannot pick up unauthorised transactions!!!

I am absolutely appalled at the don't care attitude by FNB. An unauthorized transaction went through my business cheque account on the 28 June for an amount of 267 pounds (R4800) with reference ANGLO AMERIC? I do know who this merchant is, neither have i ever authorized such payment. I have tried to log a dispute with your ***** department and filled in forms etc only to receive an SMS saying that there is no merchant communication? I do not know who the merchant is or where the transaction was performed? How am I supposed to resolve this and get my money back. This is now urgent and FNB needs to assist me as a loyal customer.