Terrible service

Dear Avis O.R Johannesburg, I have been using Avis rental for many years now and I was disappointed with my recent experience. How can you charge me with a damage that I know nothing about? On top of that I was charged for fuel yet I returned the car on full tank? This is not a way of making business. I have sent an e-mail to enquirer till today no response received. I have been calling the *** number with no success.I know you in a business but *****ing customers money is not a way of making business.