Unauthorized debit order

I just had an unauthorized debit order of R600 from FDH VLTA 82*********. I tried to dispute the debit order on my side but couldn't. I contacted FNB for assistance only to be told they cannot reverse the debit order on their side and I must contact the company. What company? I don't know the company and I have no relations with the company. I cannot believe how a Bank cannot be able to reverse an unauthorized debit order. I need this to be stopped and my money to be reversed.