Terrible service and major issues with refunds

Order placed on 19 October. Received on 2 November - incorrect item was received. I immediately queried and assisted in any way I could (Sent pictures, kept original packaging etc.) . Snatched only collected the incorrect item on 14 November and informed me they would replace. I queried multiple times to make sure they received it and when I could expect a replacement and they only rep**** on 22 November telling me the item I ordered was out of stock. I asked for a refund and immediately sent my banking detail as requested. I was promised a refund within 7 days. I am following up so often but today is 20 days since I sent my banking details and still no refund. They have my money since 19 October and are unable to help me at all! Please assist!