Hey,
I dont know if this has been posted before. Today I asked GM that I did big mistake by changing my troll into undead and if there is any possibility of changing him back to troll without paying. And by my big happines he said it is possible but you wont get your money back for it.
Edit: Oh, forgot to add, this also works with server transfers and faction change, so if you are gold seller, you can transfer there and back and sometimes they also give you back money if you say you accidentally clicked on wrong button. So yeah, gold sellers got free transfers there and back...