Worse service ever

I went to fill up at astron in airport industria, Cape Town. Waited for a while before being assisted, finally the attendant came to assist me. I asked for a fuel of R100, then he poured for R300. He then went ahead and **** to the supervisor that he confirmed with me but that was not the case. The supervisor did not even want to listen to my side of the story and they told me I'm not going anywhere without paying I should make a plan. They are pushing sales by doing that to customers as there was also another customer that they did the same thing t0