BP garage over pumped fuel, and they are not admitting that they are wrong they are saying the petrol is in my tank what's the big deal?

I had a bad experience at BP garage king williams town, I went there to put petrol for R350 and the petrol attendant over pumped by R74,00 rands and when I asked him about what he responded with a bad attitude, telling me that he assumed that I was going to fill up the vehicle, and his supervisor also gave me attitude, I asked them where can I log a complaint the supervisor said I must go to Google and this was the second time I got this experience in this garage.