No response

I order two items and wish to change them for another size. I cannot do this on line as there is no return function on my order. I have now for nearly a week tried to get hold of their 086 number with no reply (sometimes waited for 10 Minutes and eventually hung up) Sent nearly 10 emails to the customer care and customer complaints email address with no reply. Sent umpteen messages on their Facebook with no reply. There is also no customer chat function on their website as they state. What now. I will never use them again.