Read the links below about various ways to pay for items in the iTunes and App Stores.
- Add a payment method such as a credit or debit card to your account. See this link about 'Payment methods that you can use with your Apple ID' --> https://support.apple.com/HT202631 then see this link about how to 'Change, add, or remove Apple ID payment methods' --> https://support.apple.com/HT201266
- Add funds to your Apple ID balance - "Use a payment method, such as a credit or debit card, to add funds to your Apple ID balance." This takes the previous payment method one step farther by optionally using it to irreversibly add balance to an Apple ID instead of having the card charged each time.
Click here --> https://support.apple.com/HT208687
- Create and add money to an iTunes Pass - "At Apple Stores and select retailers, you can add store credit directly to the Apple ID that you use for App Store, iTunes Store, and iBooks Store purchases." - https://support.apple.com/HT203021
- Redeem your App Store & iTunes Gift Card --> https://support.apple.com/HT201209
If it insists upon a card: "Some purchases might require that you have a credit card on file, even if you use your Apple ID balance to make the purchase." - from: What you can buy with your Apple ID balance --> https://support.apple.com/HT211187
For a variety of reasons Apple will almost always require a functional payment method such as a credit or debit card be present when downloading anything from the iTunes or App Stores that isn't totally free, even if the item will be paid for with Apple Account balance. The only solution is to satisfy this requirement is to add a valid payment method.
