Return mayhem

I have bought clothes from Forever New and received delivery the second day which was very impressive, got home to fit them and one was unfortunately big. Came to work Monday called their helpline with no luck, emailed numerous times for return still no luck till i decided to go via their return system online which I am not finding any joy. I am told they don't have the size I want in stock but when i do the whole new order the very same unavailable size is available.