Avis George Airport inflated fuel charges

Avis George Airport I am fed up with your so-called refuelling charges. The nearest petrol station to the airport is Total Energies Londt Motors on the outskirts of Pacaltsdorp. When I returned a car in December, I filled up there and they even shook the car to get as much into the tank as possible. Yet you have charged me R89.99 for fuel plus a R39.15 refuelling charge. The fuel charge equates to 18.7 litres/100 km on your round trip airport to garage back to airport, when this model does 4.9 litres/100 km. Is there a **** going on? Avis Customer Care says the charge stands. You should take better care of your loyal customers and charge honestly.