Engen garages rob us

I own a Ford Ranger 2006 model from new. I stopped at Engen garage in Margate and said fill up. They managed to get 90 liters of petrol into my van. And it was not even on empty! I spoke to the manager/owner because in 12 years this is the 1st time. He said they will calibrate the pump. He phoned me a week later so say the calibration is scheduled for that afternoon,if I want to be there. I could not make it. Phoned him 3 days later, hoping they would have found the pump error. But he was arrogant and said I should have fuc&#ing been there. And by the way the pump showed a 5% error in my favor. So they actually put 94.5 liter into my 80 liter tank? I emailed Ford SA, and the reply stated that my model, if unmodified(and it is unmodified) will take 83.16 liters when completely dry, then overflow. I phoned the owner of Engen in Margate and he said fu&k me and fuc& Ford SA. And if I take this to Facebook or hellopeter I WILL get sued. The owner/manager's name is Pieter. NS: The fuel jocky said I wasn't the only one complaining. When I mentioned this to Pieter, he said what does he know, he's only worked here for two weeks.