I will never buy online again. didn't get my money back

I did not get my money back one month after I returned the product in its original package by express post with signature for which I paid 20$.
I have been contacting the customer service by phone and by email and the problem is not solved yet. this is too much

They have pretty good deals there during their flash sales. Normally I find their clothing overpriced, but it is worth getting on sale. I got a few nice pieces from them and they were good quality.