I went to fnb to reverse a unauthoriz debit order

On the 15 of April 2015 some company debited 8 rands from my account. Sunday morning i went through my fnb banking app saw the debit, so i decided to go to the bank this morning i spoke to some consultant i told him my account was debited by some company i never authorised the debit. i asked the guy to reverse the debit order and also asked him to block the debit and make my account no longer debitable he said he cant reverse the debit order theres nothing he can do about it. Can someone call me and assist me with regards to this urgently.<br>