If they're refusing to refund it I'd start a dispute. I had to return something that was faulty and they sent me another again faulty and told me to return it again and wouldn't send me another they just kept saying they had. Rather than disputing it I just left them negative feedback and they kept messaging me to remove it, and I refused to remove it until they sent me a working charger. I eventually got it and changed it to neutral. Maybe try telling them you want it fully refunded or you'll leave negative feedback and that you'll be contacting EBay. Hope it gets sorted soon x