Poor service - AVIS

Rented a car for my dad from Avis Umhlanga a few months back whilst his car was at the panelbeaters. We only realised that the vehicle did not have an etoll tag when we were returning it around 19 days later. Other than travelling within Chatsworth for most of the time, the car was used a few days a week between Chatsworth and Durban North with total mileage at 450km for the 19 day duration. Got the bill and noticed a charge for eTolls at King Shaka airport and Mooi River. Contacted Avis and informed them that the car never went near those locations as well as the car not having an etag, but consistently got messages that the tag does not have to be physically present to be charged. They completely ignored all mention that the car never went near Mooi River or the airport. At last they sent an email that the complaint will be sent to the branch, but no call or update on the matter (more than 3 months later). The amount was for a mere R103, but if I didnt use the car to those locations, then who used the etag. Sadly AVIS does not seem to be the type of company that wants to sort out the problem else they would of investigated and provided feedback.