Tokai Total Garage Overcharges

My car has a 50l capacity tank. Had travelled only 6km on reserve with a leeway of at least another 40km. Filled up and told by attendant that the tank was full and was running over. Got out to check and he put another 8l in. Pump showed that 51.92l had been pumped at a cost of R671.35. Spoke to the manager, showing him my logbook in which fillings are meticulously recorded and showed that my car had never taken this quantity - and that I always fill up. The manager was most unhelpful so the conversation became heated - then he told me that I'd been rude, but could not give any example of this. Heated, yes - rude, no! The logbook showed that the car has never taken more than the 50l capacity, but he wasn't simply wasn't interested and told me to contact the owners - Total. Only once in three years has the tank taken 50l and that was when the computer showed that only a few km were left. It is not acceptable that when facts are presented, the manager was not prepared to even consider that someone, or something was perhaps at fault.