Poor customer service from Avis with no feedback regarding an overcharge on my rental agreement

I received a courtesy car from Avis on the 30th July 2018 as i took my car in for repairs at F&F Autobody and returned the car a week later (7th August 2018) when i was told my car was ready for collection.

Upon receipt of my car, i handed over the keys of the rental car and requested if i should contact Avis, of which the owner mentioned that it was not necessary and they would deal with it.

The car was sent back to Avis by the panelbeaters a week later and i had to cover the cost for the fuel that was used as well as an additional week's cost for tyre and windscreen cover.

I have contacted Avis several times to resolve this matter and have been pushed from pillar to post and not heard anything since. This is pathetic service as i would like to have my money refunded for the charges that were incorrectly billed to me.

My rental agreement number is - E ********** 95