Terrible Service Received from Avis

I hired a car on a monthly basis with Avis Hatfield branch. On 02 October 2015, I returned a car at Grand central airport. I received a call on the 05 October from Avis Grand Central Airport reporting that the car has a scratch at the bottom of the front bumper. I responded to the lady who called me by saying as far as I know there was no scratch I made while driving the car for the duration of month. I further explained to her that on picking up the car there was no inspection sheet I signed which simple mean there was no inspection done at my presence. The amount that was debited in my account on the 20 October 2015 is R4053.96. It has been two weeks phoning Avis customer services speaking to a lady by the name of Njabulo with no success of getting my money back. Yesterday I also called and was informed by Njabulo that the Hatfield branch manager (Joenne) had said she is not going to release any money back to me. I need my money to pay my kids school fees.