Overcharged and really cheesed off

On 2 occasions goods i purchased were priced lower than scanned and charged at a till. On one occasion I bought 2 pieces of clothing priced at R199.00 and was charged R200.00. That is one rand we are talking about!! It happened again thereafter. Problem is that you don't see the price on the till whilst the transaction is in progress. It happened a second time again. If Pick and Pay overcharges a million customers one rand extra on all their goods, what do you think this does to their profit margins??? Why would they even assume that people don't pay attention or read their receipts after shopping?? Did they really think that they could get away with ****************?? If I was given the overcharged rands back, I could easily feed a few poor families. So I wonder how this problem will be resolved? How will they identify all customers who were **********? Don't tell me its the new VAT charged on old prices OR the rounding up of an amount!!!! I want an explanation and also to be advised on how I will be reimbursed!!!!