Itunes problem

Purchases are considered final as you know, but you could try the 'report a problem' page to contact iTunes Support and see if they will refund you as a one-off : http://reportaproblem.apple.com

Or you can try contacting iTunes Support via : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)

If you've looked at the purchase histories of all iTunes accounts you have linked to the card and not found it (and checked iCloud storage upgrades) : See your purchase history in the App Store or iTunes Store - Apple Support and : If you see 'itunes.com/bill' or an unfamiliar charge on your statement - Apple Support

and : About payment card authorization holds from the App Store or iTunes Store - Apple Support

contact the card issuer