Poor customer service

Good Day i am so disappointed went to buy at Russell's and only to find out that most of the items were on sale and was supposed to laybye music system of which it was on sale R4299 normal price its R5000. When i had to pay told that the price its 4700 and it was displayed as R4299, i immediately asked to see their manager and he told me that there's nothing he can do, they are human beings they make mistakes. I told him me as customer i have to buy at a price that was displayed not that on their system, thats when we had argue and i was so furious because they dont care about their customers. Russell's at Pan mall Alexandra