Pushing up prices at till

It was said on news they not allowed to push up prices but they did just that!! They advertising ultra Mel custard for R19 at canal walk and center point entrances but when you get to the till they push up the price to R31/ R32!!! Yesterday my mom wanted to buy one and the manager tells her there's no stock even though there's a few still on shelf!! So they are trying to make a fast buck at the tills and falsely advertising by the door!! Wonder what consumer protector will say about this!!!??