Snatcher ****

I ordered goods from them about 6 weeks ago. I haven't received any track & trace nr. Last week after many messages and emails the sent me a reply that they are cancelling my order due to no stock available. Then they emailed me again saying they will deduct 15% from my refund for cancellation fees! I told them there is no way they will do this. Up to now they've been ignoring me and I haven't received my refund, after I've sent them my banking details again. What should I do?