Upgraded the wrong account. refund?

Hey all,

I realized I upgraded the wrong wow account for cataclysm last week and was wondering what I would need to do to get a refund for the one I did upgrade. I'm really hoping it's not to late since it's still a (pre) expansion upgrade.

Thanks!!!

(I'm aware I'll probably have to email/call someone - email preferred, however I'm not finding a good place of where to start so I figured I would post this)