I have accidentaly bought and equipped wrong item Is there any chance to fix it?

Hello,

this happened on Frostmourne server.
I was farming every day for the past 14 days to afford the Darkmoon Card:Greatness for my hunter called "Fasterka".
Today was the day i have finally saved enough gold, so i buy the Darkmoon Card off AH and equip it proudly, celebrating
the moment cheerfuly, only to find out I've bought a wrong version of it.

(I didn't know there's more version, my friend just told me save up enough gold and buy one >.> )

Now, is there any way to fix this or am I doomed?

There is no support for items obtained in game.