incorrectly billed

I received goods from home choice which I did not order so I phone to ask for that order they told I ordered that online of which I did not ,so I was asked to post the goods back to them and was told that they will refund me for my postage ,they still haven't paid my money back instead they now telling me that I owe them for the second order because according to them I ordered two items I only returned one ,I told them I never received a second item ,they told me it was received by a third who claim to be my brother.please help I know nothing about this goods I'm also not staying with my brother.