AVIS charged for dent I am not responsible for!!!

I hired a car from AVIS on the 21st of August, 2015 in CT Airport. We were originally supposed to get a Chevrolet Spark, but got upgraded to Ford Figo. We got keys to the car, and that was it. No one came to inspect the car. Then I noticed that some damages around the driver's door, and around the car. So I took pictures of these and called one of the Avis guys to confirm the damages we detected. The AVIS employee did further inspect the car, he simply recorded the damages we detected and we were on our way. On returning the car on 23rd of August, AVIS decided to thoroughly inspect the vehicle. The inspector told us there is a slight dent on top of the car. So we logged a complaint for AVIS to investigate the matter because I was not responsible for the damage. I requested for the proof of logging the complaint and detailed report of the damage but I have yet to receive anything. I got reference no: 15/95390. I have been calling AVIS on ***, but no one picks up. I have already been charged for the dent (R3300). This is very unfair because I have objected to this claim from day 1. So I want someone to please contact me asap because I am not impressed with AVIS right now.