Charged for petrol on a fuel tank return

Good day<br> <br> Booking 10D5Z5 <br> <br> I hired a rental vehicle from 24 -26 July. Returned the vehicle on time on full tank on Sunday 26 July. I filled up the car at the Engen garage right opposite the East London airport which is not even half a km away from the rental office. I received my deposit with a R97 petrol charge. I have called the call centre, given run arounds. Worst service ever, it is infact a **** - had I not been vigilant in checking my charge what would have happened? I have proof of petrol slip with date and time also on bank statement as I paid with speed point