I’m getting charged extra for iTunes

iTunes is an application and is free so you must be talking about something else. It is difficult to answer your question without knowing what that is. Start with the information in the next section:

If you see ‘itunes.com/bill‘ or an unfamiliar charge on your bank, credit card, or debit statement - Does not mention purchases made under Family Sharing which might be charged to the organizer's card but will not appear under the organizer's purchase history or subscriptions. Ask family members about those or check your receipts. --> https://support.apple.com/HT201382