Car Rental Company Overcharged

When my car broke down, I contacted BMW Assist and it was towed to BMW Sandton. The service from BMW Assist was good up to this point however the car rental company they use, Woodford Car Hire, overcharged my credit card for the fuel I used. I did about 30km with a 320i and they charged me R280 for the fuel! I took a photo of the petrol gauge to prove this. When I complained to BMW Assist, nothing was done about it and I am still waiting for a response.