Overcharge on invoice

I was charged for fuel after I refilled the car and returned it to Europcar King Shaka Airport. Upon returning the car it was checked for damages and that the car was full. The employee confirmed the car was full and that I would not be charged for refuelling the car. When I received the invoice I had been charged for R80 of fuel, an amount which is more than I filled the car and an amount which would be impossible to fit in the tank since I had already filled it!

I queried it and the branch contacted me. They said they cannot help me unless I can prove that I refuelled the car. This branch is out to cheat and make a quick buck. Avoid them at all cost