Zando's flawed return policy

I ordered a dress that was delivered in the wrong colour and without sleeves as I had ordered it. It was an international purchase; so a

Upon arrival at the warehouse, I was informed that it did not have sleeves & I accepted to take it without. But when I got the dress it was in a wrong colour. I requested a change of item or refund. I have now been told that I have to pay for courier services for returning the dress, though it is Zando's mistake to send the wrong colour.

I find it totally incorrect as I didnt participate in the mistake Zando made. I have send photos they requested as proof of wrong item, but I am still expected to pay for sending the dress back.