Who pays for the return postage

[akkmma]

Hi there, 

I bought something from a private seller, who offered free P&P. The item wasn't as describe, so I requested a refund (has soe flaws). Choosing for a reason 'it doesn't match the listing'. in order to receive my refund I had to pay the postage.

Soon after that someone requested refund from me, but it turned out that I - the seller in that case -  have to cover the return postage. I was a bit confused, so I read through terms and conditions and it states there, that if there's something wrong with an item, the seller covers the return postage. Which makes me thing that in the first case, when I was returning an item, the seller (not me) should cover the postage fee. Was I tricked to pay it (I'm fairly new to eBay) or did I trick myself by selecting as a reason 'it doesn't match the listing' rather than 'there's something wrong with the item'? Or is it because the seller offer free P&P, that I had to cover the fee?

Can anyone clear that out to me?

I'd appreciate.