Bad customer service

Went to pick n pay jackal corner to get me something to eat. Took a lucozade from the fridge which had a price of R8. 99 and I get to the till to my surprise the 15.99, so the cashier asked the supervisor for an override. Supervisor gave me attitude asking me if I saw it at that price so I said yes, I then I said to her we need to go check the price. We get to the fridge the price is indeed R8. 99. She then told me it's for still water, I then rep**** and said, it's not my duty as a customer to be checking for barcodes if they match, I take what the price says. She then escalated the matter to her manager, who also asked if the barcodes match, I said to him as a customer it's not my duty to be checking for barcodes if they match. They should address the matter with the merchandiser. As hungry as I was I left the shop with nothing. Never had this kind of treatment in other retails, why pick n pay jackal corner?