Sissyboy ignoring me

I ordered a size 4 flat beige sandals from Sissyboy online on the 19th of January 2018. A week later I received a high heeled denim size 6. I informed them right away of the incorrect order and I was promised that they will send Dawn wing couriers to fetch the incorrect order. 3 weeks later I am still waiting and they keep making empty promises. Yesterday I emailed them and requested my refund as they failed to deliver what I ordered or to rectify the mistake they are ignoring me. I feel helpless as they have my money and I don’t have what I ordered. Worst service, just want want my money will never do the mistake of ordering from them again