Family sharing: I’d like to use my own credit card
I don’t understand why my husband has the Share Purchases with family option disabled but I still can only use his credit card. Help please!
How to share purchases with your family - Apple Support
See the part about turning off purchase sharing.
Sometimes it helps to sign out and back in again so the device takes a fresh look at configuration settings.
If you still have questions or problems:
Contact Apple. Click here --> https://support.apple.com/choose-country-region Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world."
Click here --> https://support.apple.com/HT201232