Money owed to me

I rented a vehicle from Avis King Shaka from the 29th of Jan till the 1st of Feb 2015, reservation number 3***-ZA-4. The amount quoted was for R816.00. On arrival an amount of R1988.95 was deducted from my account, explaining to me it's just a figure they deduct in case something happens and for fuel. I returned the vehicle with only quarter of the petrol tank being used. On providing the vehicle back, I requested an invoice to be supp**** to see what the charges would be for the fuel, therefore, to see what the overall cost would be. I doubt that the associated cost for the petrol will be over a R 1000.00. Therefore, I would like to know when I will get the balance owed to me back, as well as the indication of the cost for the fuel. I think it's pathetic from Avis to take money and according to the consumer act provide information reflecting what the associated cost would be.Also, getting fed up in renting a vehicle in the B group and getting the cheapest group vehicle. I would like to get a breakdown in the cost and money owed to me back into my account.