When you have been charged twice for same item, how do you get your money back?

Morning Domangere,

Thanks for using Apple Support Communities.

Following this article refund will be an option.

For more information on this, take a look at this article:

How to report an issue with your iTunes Store, App Store, Mac App Store, or iBookstore purchase

http://support.apple.com/kb/ht1933

Best of luck,

Mario