online out of stock - no refunds

I ordered something online on 6 February. 14 days later they let me know it was not in stock and they would refund me. 8 days after that they tell me they can't refund to my card and to send bank details. I send them the next day. That was 12 days ago. I am still waiting for a proof of payment. I have sent multiple emails and received one reply and one call back.

Builders have had my money for nearly 6 weeks.

Please just refund me