Boycotting PnP Fish Hoek

I will never buy at PnP Fish Hoek again. I went to to buy Hot chocolate and it was displayed for R67 and I took it. As a customer I see the price displayed in BOLD and take the it. When i got to the till, the price is twice the amount. They checked with me to confirm and then called the manager as i showed the staff the issue. According to my knowledge they must give it to me for the amount displayed, and no where on that display area had a tag for the specific item i wanted to buy, and again directly under the item Showed R67, but the Manager tmis telling me she can not give it for that price. Who is to blame for that mistake as a customer I take the item for the price displayed.