Deposit not refunded and Charged for fuel but the tank was full

I hired a car (VW Polo) on 10 Sep and returned it on 14 Sep. I filled the fuel tank at the fuel station at the airport and dropped the car off 2 minutes later, but they deducted money from my card and said they filled 12 more litres of petrol in the tank 😳. From 14 September and now it is 14 October and they have stills not released my R7000 deposit but they have taken what is due to them within a week.. The people are ****** and I will never recommend them or use them again..