Bad customer service

I was at studio 88 forest hill I wanted to buy Red puma foam for R799 I saw it on the displays with that price when I go to the terminal the cashier said is R899it was a mistake he can't give me with that price because he is going to underbank. I said to him the price I see is the one I have to pay he said is impossible because is a mistake. He said m gonna give you your money back and you will buy it at other stores. His name is **** and he said is a store manager and I have a proof of that.