Client to pay for company's false petrol claim

I rent a car from them.<br> Upon return I had the car's petrol tank filled to the brim, saw it with my own eyes as did the petrol attendant. Had only to drove less than 2 km to hand it over.<br> To my surprize I was charged for and additional 10 litres of refuelling petrol on the bill I received !<br> I tried through their system to explain and state my case. Even supplying them with my slip's. <br> They - in the person that attended to my complain - refused to accept my explanation and confirmation and stated I was not to have filled up the car.<br> Had I NOT done so, I would never have had the evidence that they stole petrol from their clients, would I ? How would I have been able to address this issue had I not had the car filled up myself?<br> It's quite obvious they de***** their clients and that they are not even willing to address the issue.<br> Apparently a Chev Spark's petrol consumption according to the person is in the region of 12.5km / litre.<br> Wow!... Amazing expensive car to drive isn't it?