Hacked

Well, I suspect you already know that since they added an authenticator, that's pretty much solid evidence they are into your email account.

This has already been reported - and since they were online, I've asked this account be locked so they can't cause any other mischief at the moment.

At the very least you need to secure your system - and most especially your email. I'd actually recommend making an entirely new email account from a known secure system and changing your Battle.net.

Normally we send emails on this, but since they are into your mail, they'd just grab the new information.

The best course in this situation is probably to make your new email - call Billing to update it, then proceed from there. Naturally, you'll need to make sure your system is also secure.

This may prove useful.

Account Hacked? Security Issue? Look Here!
http://forums.worldofwarcraft.com/thread.html?topicId=24702231244

You may also want to look into getting an authenticator for your account. It's no substitute for good security habits, but it will help keep them out of your WoW account.

Blizzard Store
http://us.blizzard.com/store/browse.xml?f=c:6

Mobile Authenticator
http://us.blizzard.com/support/article.xml?locale=en_US&articleId=26109