Avis **********- debiting my account.

I had an accident and when my car went in for repairs Avis lent me a courtesy car I gave them R1500 holding deposit and the guy told me to punch in my banking details on his phone on the Avis app so i can get my deposit back....I took the car back last week monday. Yesterday morning when i wake up i get a debit order from Avis on my account and now one told me about it now i have bank charges as there was no money in my account. I called them and spoke to a very impatient lady Thuli she told me the rules have changed they debit clients for whatever they used while having the rental vehicle but no one told me about this they just debited my account. Last time i rented a vehicle when they refunded me my R1500 it was less what i used so thats what i was expecting. Can you guys please pay those bank charges i have never had my account on Minus now you guys have messed up my account.. ***5ZA4