Avis claims you are being unfair to me

I paid a deposit to Avis using my FNB Card on 17 June. I returned the car back to Avis on 20 July. Since the 20th of July, I have been waiting for Avis to release my deposit back into my card. Avis even debited my card with some R150 while FNB is holding my R1,500 on their behalf. Today Avis tells me that I must take it up with FNB, they claim they issued an instruction to FNB last week already to release my money back into my acc. I now don’t know who is who in the zoo, whether Avis told me the truth that FNB is not releasing my deposit.