Buy one item get another

I purchased an 8L crisp air fryer for R999. (with glass front panel). They had 2 similar items listed at the same time the other was a 4.5L air fryer with solid front for R600. Although I ordered the more expensive bigger item they sent the cheaper Item. I logged a complaint on day of delivery. I received a response 5 days later saying the two items were the same. Even when I sent them photos of my item and links on their website showing the mix up. They are now refusing to assist