Best Dress owes me money

I ordered a jacket from Best Dress when I received it a month later it was the wrong color. I sent it back and asked for a refund for the jacket and the post office costs that I had to pay for their mistake. They said they will pay me back, it is a month later and I don't have the money and they don't reply to my emails. I'm very disappointed at this type of service since it was my first online shopping I did and now they owe me a lot of money.