How can I find out why I have monthly charges from Apple/iTunes on my credit card?
Apple has instructions for your situation located at itunes.com/bill:


Compare your purchase history with the charges on your credit card and bank statement.
Check the status of your subscriptions.
Check all of your Apple IDs.
If you share your device with others, including young children, learn how to manage your password preferences.
Anyone who has your Apple ID password is able to make charges to your account. If you have unauthorized charges, change your Apple ID password.
If you compare your credit card or bank statement to your purchase history and still don't recognize the charge, contact Apple Support. If you don't use your Apple ID to make purchases from the iTunes Store or App Store and see charges on your statement, contact Apple for help with Apple ID account security. If you think you're being billed twice for the same item, it might be a payment authorization hold and not an actual charge. The charge will disappear after your purchase clears.


If you have followed all these steps, there may be a possibility that your card number was stolen. Call your bank and dispute the charge. Do note that if this purchase was indeed done on one of your accounts and you do a chargeback, you risk getting locked out of that Apple account.