Avis stole my money

I rented a vehicle from Avis and paid the deposit in cash when the vehicle was delivered to me (3 days after promised) When I returned the vehicle I was charged an additional R825 rand in stead of reimbursing me with the balance of the deposit made. I was not reimbursed at all which means I paid R2 025 over and above the rental costs (covered by my insurance) I called every day last week and spoke to a Tsepo, Nhlanthla, Phillip, Cindy and two other call centre people without an joy. No one has bothered to call me back or send me a email. Nothing is being done to my query - Avis stole R1200 from me