petrol stations charge what they like

could you guys please confirm that your petrol stations can charge for fuel what ever they like , and inform us that the price of diesel is not regulated . We were in Clarens this weekend and got charged badly and were told they can charge what ever they like its not regulated . Is this true , and if so people rather fill up in Bethlehem when going out that way , Clarens is not scared to nail you because they know you need to fill up