Please bring back my money

I went to collect my rental car at Hoedspruit Eastgate airport Avis after Miway has reserved a car for me. When I arrived at hoedspruit I was told to pay an amount of over R5000 for deposit. I was given the car which I have used for 30 days. I have then returned the car at Avis Menlyn with a full tank and good condition. Avis then deducted an amount of just over R3000 in my credit card. I have been waiting for Avis to pay me back my deposit of over R5000 and when I enquire about it, they keep on ignoring me. I have called several times and no one is helping me.