1) Open the Settings application
2) Profile (your name at the top) - [iTunes & App Store OR Media & Purchases]
3)View Account (It may ask to put in your Apple ID password)
4) Then look at "subscriptions" and "Purchase History" FYI sometimes subscription isn't there and that normal
5) Check to see if you see any unauthorized purchases
6) If you have unauthorized purchases go to Settings - Profile (your name at the top) - Password & Security [Make sure Two Factor Authentication is turned on AND make sure that the "Trusted Phone Numbers" you see are numbers you recognize.
7) Once Two factor is ON go to "Change Password" and change your password AND select "Sign out of all other devices" once it prompts you at the end after you change your password.
8) After you change your password call Apple and tell them you have unauthorized purchases and to have you transferred to iTunes department.