No accountability for excess charges

I recently rented a car from Avis (PE airport). I sustained one smallish windscreen chip, thrown from a truck, no cracks. When I returned the vehicle to Cape Town Airport, I several other small windscreen chips were pointed out, as was a small stone mark on the front bumper. All were blamed on me because they were previously not recorded. I have been charged R8864.13 for "Accident Repairs / Renter Liability" with no further explanation. Several emails to Avis customer care (12 Oct, 22 Oct and 7 November 2018) have resulted in promises of explanation to come, but no explanation has been provided to date. A review of the rental agreement specifies that 1) fair wear and tear is included (surely a small chip is wear and tear - Avis appears to have charged me for a new windscreen for one chip) 2) There is a massive discrepancy in the vehicle mileage description: the Rental Agreement incorrectly says that the car I hired had 3717km on it at the start, when actually it had 32558km on the odometer - correct on the rental RECEIPT (ie are your records wrong and charging me for nearly 30,000km worth of wear and tear?). Do they really think that a car with over 30k km on the clock will have no marks at all? All of this has been pointed out to Avis but I have had no response.

It appears that Avis expects the renter to check the cars for them, rather than the company actually doing due diligence checking vehicles. If Avis' processes were transparent and seemed to be done properly, I would unhappily suck up the exorbitant windscreen damage charges - but they are NOT transparent, and it appears to me that your vehicle checking processes are wrong - placing the burden of proof on the customer. I will not use Avis again.