These are user-to-user forums, nobody on here will know what the charges are for.
You've checked the purchase history on your account (Store > View My Account menu option on your computer's iTunes), and have you made any in-app purchases or have any auto-renewing subscriptions ? If not then you can contact iTunes support via this page : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption