SuperStep Is Not Issuing My Refund

I ordered a pair of Birkenstock slippers from SuperStep, but I was sent a pair of Adidas men’s shoes instead. The packaging was clearly mismatched, and it was obvious that no quality check had been done before shipping. Due to this mistake, I had to pay for shipping twice and have been seriously inconvenienced. Despite returning the item, my refund has still not been processed after 13 days. I have contacted SuperStep customer service multiple times and have been repeatedly told that the refund will be issued “as soon as possible,” but I have yet to receive it. This level of service from a major retailer is unacceptable and has left me deeply dissatisfied.