Wrong prices under the wrong stock and being made my business as a customer

Goodday I just walked into this Game store in Watercrest to purchase Jacobs coffee the store had the wrong price under the box I wanted to buy and I dnt know that until im at the till.They refuse to give it to me telling me it's my duty to look for barcodes I dnt work for Game I'm a customer who brings the little business that is needed...The wrong price is under the wrong box and that price belongs to stock that not even on the shelf. The manager says it's my responsibility to look at the barcode but I dnt work for you guys. And I still want my coffee for the price it was under,u Your Game stuff should do there jobs and put it under the right stock.I will be glad to be connected about this being so that I need that coffee