So yesterday we killed Ultraxion and finally got my chest piece but I accidentally bought the wrong one (the elemtanl one instead of the resto one). So I wrote a ticket about it, this had never happened to me but my friends reassured me that it was still possible to get the resto piece instead because it had happened to them a lot of times before. I could not sell it again because it already been transmogrified, gemmed and enchanted.

The GM then answered me with "Sadly, because you can use the in-game system whenever you buy an item wrongly to sell it back for a full refund, we no longer offer item refunds or swaps for any reason."

I did not even notice it was the wrong piece until I wanted to test out my new set bonus, that is... too late to sell it back. I wouldn't even be that pissed off if it wasn't the loss of the 4 set bonus which would help me a lot with healing. I'm not even sure why I am writing here since apparently it's a breach of "Intentional Game Mechanics" that the GM also said.