Builder's bad service and money **** at the till

Every time I buy from Builders at Castle gate, I get done in at the till. They **** you with the price advertised and when you get to the till, it's more than double.Now you have to take the shop manager all the way to the rack and show him the wrong prices. Then he looks at you.... And says nothing. So I told him I experience this every time in every builder's. Also told him I will take my business to Chamberlains I will never enter a builder's again and make it my mission to tell friends and family how they **** you at the till and bad service.