istore pre-owned ****

I bought an iPad from iStore Pre-owned and they delivered the wrong device, I have called their customer care and when I got through to them they said they don’t have the device I bought in stock and asked whether I wanted to keep the wrong device or get a refund and I said I want a refund and they said they would process the collection of the wrong device and refund me however since then I have called so many times trying to get the iStore Pre-owned to call me and tell me when they will collect the wrong device and refund me my money however they have not called me back or emailed me or communicated anything and I can’t even get ahold of them.