They made a mistake, but I have to pay more money to fix it?

TLDR; I purchased a product at a discounted price, was sent the wrong product, told that the product I actually purchased is out of stock and I must pay more if I want a replacement.

Purchased a product on black Friday for a discounted price. I was then sent the wrong product, and when I tried to have the correct product sent to me, I was told that it is out of stock at the price I paid for it and I must pay the current price that is on the store. When I tried to call them and query if they could credit me the difference, I was told that they don't honor prices and that they will not help me any further. So basically they made a mistake by sending me the wrong thing, but now I have to pay an extra amount?? Completely absurd, I can't believe a company handles their customers this poorly, no wonder they are scared of Amazon coming to SA.