********** Transactions on my account ignored by FNB

I had a ********** transaction on my account on the 4th of March, I immediately logged this with FNB and i was advised to block and destroy card. I was then sent dispute forms. I submitted the completed forms. after a month, I was told that there is nothing they can do as I need to submit proof that I canceled the transaction with the merchant. I tried to explain to them that i did not buy anything it was a ********** transaction. I was advised that the ***** department will be in touch, 11 days have passed and FNB is just not helping me. I told a colleague about my frustrations, she advised that the same thing happened to her and she was assisted the same time. I dont know what to do anymore.