Most of the people on these forums, including myself, are fellow users - you're not talking to iTunes Support here.
You can check the purchase history on your account via the Store > View Account menu option on your computer's iTunes, though I'm not sure if that shows auto-renewing subscriptions. If you can't find where the credit has gone 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
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