Avis Inspect car, no damage, later claim there is damage.

Rental agreement E ********** 03 I rented a car from Avis on Friday 27 July on OR Tambo Airport. There was no damage to the car when I returned the car on Sunday morning, 29 July. On my return the car was inspected thoroughly by an Avis representative. There was NO damage confirmed. Later the Sunday, I received a call and someone from Avis asked if I am aware of a small scratch. I said that I'm not and again said that the car was inspected and there was no damage. However, I smelled a rat when I received an sms which says something about R1300 odd damage. I called Avis and asked for the invoice. They said it's not available yet. Email them again. And they rep**** that I must call the branch. I was already irritated by the poor service and asked them to call me. They rep**** someone will call me which never happened. Now I received an invoice and more than R1300 is added for "damages". This is absolutely nonsense as the car was inspected and confirmed everything was in order, I dispute the damage and if there was a scratch, I must have been after I returned the car. I require an apology and a new invoice without the damage.