WotLK Item Missbuy

[Flickblz]

Hi, my character Blackrock - Fxckblizard, just bought wrong hat [Cowl of Malefic Repose] , witch as same as mage's pve set [Sanctified Bloodmage Hood] but WITHOUT set bonus, can you help me change it to [Sanctified Bloodmage Hood] ?

[Persivaln]

For such reasons there is 2 hour in-game period to return item back to vendor.
Also, only PvP set keeps bonuses over tiers, PvE sets are separated and doesn't interact with any other set