Refund on undelivered order ***

I bought 2items on Online and 1was delivered successfully. With 1one I was told it is out of stock. Payment had gone through already. I had received an email saying that I will be sent a voucher as a refund because I had paid through an EFT not a credit card. I responded and said that I need cash back because I want to buy the product elsewhere as Mr Price could not provide. I cannot buy the product from a different supplier with a Mr Price voucher. I sent through the bank details requesting for a cash back. There was no response. I went to the nearest branch to try and resolve the issue thinking they could maybe exchange the voucher into cash. I was told they are two different entities. They called the Online branch and they had promise I will receive an email to respond with my bank details and I am still waiting as we speak. The order was someone the 14 Dec. Please advice on what to do further. I have all the emails as proof.