Continues debit after return of the car

August we rented a car through Avis for a month. on collection we paid the amount needed for rental. On return, I was told I must paid money for kilometers to close the rental, which I did. However, a week later, Avis debited my account again with an amount close to close to both money for rental and kilometers. I went to enquire to the branch 70 Francis Baard Street, Pretoria Central, the lady I got told me its etolls money. I asked them proof of the toll charges and that no tolls that can cost close to 8K as if the tolls cost equal to a kilometer. The manager was not there to help. No one bothered to help. I have emailed their customer help, but no no bothers to call or email back with explanation. It is a terrible experience I am having. My first time hiring a car with this company and already I am regretting.