Appalling service and no refund received

I ordered a product online. For 7 days there was no movement on my order. Then someone phoned me and told me my order was cancelled - without any reason. On enquiry I was told that there was not stock anymore because the online stock and store stock is the same, and someone took my order in store. Since then I have been following up on my refund (which they say was backdated to 18 November) but I still have not received any refund. In one email I was told to send my bank statements for the past month so they can make sure I have not received the refund (which is ridiculous as my bank statement is private). An email was then sent to me saying my refund was processed on 18 November. My emails have been ignored for the past week, now, I have requested a proof of payment, but still I have not had any response.