Bad quality on goods

I ordered sneakers via WhatsApp from Christos Clothing (online trading) ( ********** ) on the 04th Dec 2017. And they delivered the order on the 08 Dec 2017 as per agreement. I lodged a complaint later that day that I wasn't happy about the quality of the sneakers, i asked them to exchanged them for All Stars, they ignored and didn't deliver and ended up wearing sneakers, after 2 days I wore them they were worn out. I send them a pic of worn out, they offered to change it with a different type of sneakers, which I agreed to, when they delivered it again I showed them the ones (same as the one they were exchanging with) theirs was ****. We then agreed on getting a refund. Since today I haven't get my R1100. They've been lying to me, promising to refund and now they ignore my WhatsApp and calls... please assist