See your purchase history in the iTunes Store on a Mac or PC - http://support.apple.com/HT204088 - Does not include purchases made by others under Family Sharing; those have to be checked from their accounts.
If you see ‘itunes.com/bill‘ or an unfamiliar charge on your bank, credit card, or debit statement - https://support.apple.com/HT201382 - "Before you contact Apple to request a refund for a charge you don't recognize"...
If neither you nor a family member (if applicable) has a record of this purchase and you only saw it on a statement for a credit card you alone control, contact your bank or card company about card fraud. Apple does not handle that.
Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - https://support.apple.com/HT204084
Report a Problem - http://reportaproblem.apple.com - "Sign In for help with iTunes purchases made in the last 90 days"
Other ways to contact iTunes Support:
https://support.apple.com/contact
https://www.apple.com/emea/support/itunes/contact.html