Ripping of customers

We normally like to shop at the Checkers Hyper here in Plett but now I have had 2 bad experiences of incorrect charges. I shopped, a couple of days ago and purchased some goods. Some were on special while others were normal prices. At the till the prices charged were higher than on the shelves with 3 different items, one of them being mushrooms.. Price on the shelf R21.95, price rung up R22.95. The supervisor arrived to correct the prices, called a lady out of a office and told her that the prices were incorrect and must be fixed. Yesterday I shopped again purchased mushrooms. The price on the shelf was still R21.95 and I was charged R22.95. I also purchased a 2ltr Oil, which, on the shelf had a special s sign advertising the oil at R43. The till operator charged me R51. I called for the supervisor again and she said that it will be fixed, same words as before. I was held up at the till for 10 to 15 minutes, on both occasions, waiting for the supervisor and a runner to get the prices off the shelves. I just feel that this is poor practice and wonder how many people have been ********** with the incorrect pricing. I do purchase a lot as we run a guest house and need supplies. Will be buying more at Pick 'n Pay from now on.