Avis helping themselves to my bank account

I have a mini-lease with Avis, for a class A car. I had a small accident about 3 weeks ago (not my fault) and was informed by text message a few days later I was being billed about 14,000 - a huge amount of money, and way over the top, equal to about three months of my rental charges. I refused Avis permission to take any money until they could fully explain the charges to me - after weeks of receiving no response to emails, Avis went ahead and took the money. How can you take someone's money when they explicitly refuse you permission? Can big companies really act like this?<br> <br> Then, this morning, I finally received a detailed and informative response to my original questions regarding the accident - and checked my bank balance to find Avis have taken another 1500 euro (21,000 rand) with NO explanation. I have absolutely no idea what this is for and of course no one answers the phone when I ring my local Avis office. I had to ring my bank and ask them to halt all future Avis payments as it seems at this stage Avis are just helping themselves to my bank account. They have taken about 35,000 rand in the space of 1 week. I want this latest charge of 21,000 rand refunded immediately.