Disgusting service, rude staff and false advertising

I went to purchase groceries at this shop. An item was priced R19.90, the cashier scanned it and a lady who was standing at the till took it and went to change the price to R94.17. There was no communication with me, they then tried to scan the higher price and I queried why. She told me it was the managers decision. I spoke to him, he was rude and abrupt saying it’s not his fault and I must pay the higher amount or leave. The rudeness and lack of customer service was appalling, and I was told if I have a problem I will need to come see the owner at 1pm. How do you put incorrect pricing on items only for you to change without consulting or communicating with the customer?