Unhappy customer

I visited a Pick n Pay store at Honey Junction, I picked a redbull energy drink on a price that showed R26,99 when I got to the counter it scanned R34,99, I told the cashier that the item was on a price of R26,99, she called for the supervisor nd they refused to give me the item on the price I saw on the shelf, the supervisor even said that she won't argue with me, even though they still saw the price on the shelf, the supervisor is clearly showing bad and poor leadership. I was not happy with the service they provided.