Who pays postage?

I received an item a phone case and it was far from the description,

 

wrong case completely. I told buyer it was wrong and they wanted

 

me to send it back to China and they will send another free,

 

**bleep**??? I want to know please, Who pays for the shipment back

 

when it was not offered by seller OR have i missed something in

 

the "Fine Print"

 

by seller?