What happened to paying the price you see?

I went to buy a packet of chips at Pick and pay and upon reaching the cashier, the price was different from the price that was displayed. Upon my complaining to the cashier about the difference which was three times more than the displayed price. She called the floor manager who verified that with me and told me that I should have verified the price displayed with the barcode on the packet. She sent me to the guy who was the store manager on that day, who then told me that the packers might have made a mistake and he was sorry that there was nothing he could do about it. The same thing happened at Pick and Pay, Village Market, and I was made to pay the displayed price. The store manager's attitude towards this matter was very arrogant.