Claiming damage to a vehicle which was in perfect condition on return...

Rented a car from Avis for a December holiday in CPT. Upon return of the car to Avis at the airport, I was informed that we were “good to go.” Months after the fact Avis have now put through a debit of over R2000 for damage to the vehicle. I have been disputing it with them for almost two months now and have not in anyway been assisted. I have emailed both the branch manager and returns manager and received no return communication! Utter *******!