I posted this in customer support, and the blue post directed me here. Reposting what I said there:
I currently play both WotLK and Era.
I have one active account (WoW1), and one inactive account(WoW2) that I have no intention of reactivating right now.
Every time I swap game version (wotlk <-> era), my account changes to a random account (i.e. including the expired one).
It is annoying the crap out of me.
Short of deleting the account, is there anything I can do to prevent it from swapping to WoW2? No matter how many times you swap me to WoW2, I am not going to be adding game time to it right now.