Need to sort out pricing

A few months ago I emailed Food *****s regarding the pricing of their bread rolls. The price for 4 Cheese or Savoury Rolls had a small discount. Unfortunately at the cash desk the undiscounted price was rung up. After about ten weekly visits and having to call the supervisor to sort it out I stopped using Bothasig store. I emailed F.L.M. and they promised to get back to me. Nothing Received. Yesterday (19th Ten Buck Tuesday) I went because Mushrooms were on a special. Whilst there I bought 4 Cans of REBOOST on Ten Buck Tuesday. On checking the receipt I was charged 4 x 11.99 = 47.96, with a promotional discount of 5.97. That equals 41.99 which equates to 10.497 per can. Now 50cents is not a lot, but it is 5%. How many people check their till slips, and the majority of South Africans will not complain anyway. FLM need to sort out their computer system.