Pick & Pay wrong prizes

Bought Organics at Bonaero Pick & Pay it is on special but when you get to the till you get charged more. I went to manager they first said it is correct until I showed them and then they told me it is head office that controls their prices and had to wait about half an hour to get my money back that is unacceptable. A lot of people do not check their slips so how many people do they ***** money from. And it is not the first time