wrong dress delivered - please help

I ordered a dress from best dressed on-line at the end of June. The dress I got delivered, was not the one I ordered, it was not even a dress, it was a matching top and skirt! I e-mailed customer services, and explained what had happened. I was told there was no point in returning the goods, due to delivery costs, as it came from China. I was then told I could get a partial refund, but I requested a full refund. Since then, despite sending several e-mails to ask what is happening, I have not had any replies. What can I do next to ensure I get a refund?