Terrible after sales service

The after sales service is the worst that i have ever experienced. The product is received was of a poor quality and i returned it with a promise that as soon as the item is in their possession, that they will process a refund. They initially indicated that they will process a credit note but i insisted on a refund. Item was delivered at their premises on 11 Jan 21. Since then i have requested my refund 4 times already. Now that they have their item back, they don't respond. I have now paid for an item that i do not have and had to pay the courier for collecting and delivering it.