Engen - Rude attendant and general manager who doesn't listen

I just went to an engin garage, bloemfontein, Northridge engin garage. I went to go throw in petrol. I told the attendant I want 150 he showed me 500 with his hand I said again 150 he proceeded to throw in the petrol he went past 150 and I stop him 269.80. We went on saying I said 500 if he didn't talk to his colleagues he would have heard me. The general manager was rude aswell saying it will.cost him 3500 to get the 5 litres of petrol back and it would be an hour and I was I would wait telling me I just wanted free petrol I'm greedy. If I wanted free petrol I would have stop them I even said I will wait for the hour for them to get the petrol out they didn't want to. I love engin either all my heart and in 11 years is the first time I'm treated bad the most disgusting service and that for a General manager. I've worked for Engin for 4 years and not ever have I seen my General Managers act like that when encountering problems or issues and we have had really bad situations. But the GM was always cordial. You must teach your attendant to communicate properly and stop speaking to other staff when busy with a client seriously