Apple balance not being used.

This article outlines what you can buy with your Apple Account [Apple ID] balance --> What you can buy with your Apple Gift Card or Apple Account balance - Apple Support

• "Some purchases might require that you have a credit card on file, even if you use your Apple Account balance to make the purchase."

• "Where the Apple Gift Card is available, you can use your Apple Account balance to buy products and accessories at apple.com or in the Apple Store app."

From: How apps, content, and subscriptions from Apple are billed - Apple Support

Apple Gift Card and Apple Account balance can't be used for some purchases

• You can't use your Apple Account balance to send gifts or gift cards.

• For some recurring charges, like AppleCare+, you can't start your subscription with Apple Account balance. But as long as you keep another valid payment method on file and your Apple Account balance would cover an entire charge, your recurring charge will pull from your Apple Account balance.*

• Some subscriptions might not be charged to your Apple Account balance.

• If you use Family Sharing, your family members can't spend your Apple Account balance. Funds that you add to your Apple Account balance are available only to you. Learn more about how purchases bill to your Apple Account balance.

Your Apple ID balance is ONLY used for Apple services that are billed directly to your Apple ID.

Several types of charges ignore your balance and go straight to your backup payment method, even if your balance is large enough.

This is why your card/payment method is still being used.