Guild Wars 2

I just bought a Dungeon piece wich i already had, so, suggest me what to do with it, it seems i cant get a refund and im not interested in lvling another toon just for him to use it.

As you said, there is not refund and no way to get it unbound so you might want to salvage it instead of deleting it to get a litle bit out of it. But my advise would be to keep it in storage and use it if you find the need to use different stats (runes or sigils). You might not yet have had the wish to have different runes in certain situations, but you might in the future (for example, when fighting the firegolem in Sorrow’s I would like to have 2 superior sigils of melandru to have less conditionduration on me).

You could try making a ticket with ArenaNet, I don’t know their policy so it might not work. Otherwise salvage and hope for the best!