Pathetic Service

Visited the store to purchase groceries. Parmalat yogurt was stacked on a shelf with a price tag below it reading as R12. 99. I get to the till and the cashier rings the yogurt up for R16. 99. I question her and she says the incorrect item was placed on the shelf. Is that now my responsibility that the staff have failed to do their jobs? Am I not to pay the price marked as seen on the tag? Do consumers now have to verify price tags and barcodes before making a purchase? I asked for the manager and the cashier and supervisor played ********, they refused to answer me. I waited but no manager arrived so I left. Pathetic service.