Apple Support

To pay for apps and in-app purchase items, users will need to link a valid payment method to their Apple ID account.

Alternatively, funds may be added directly, as account balance (like store credit), through transfer or Gift Card.

Payment methods that you can use with your Apple ID (by country) - Apple Support

Add a payment method to your Apple ID - Apple Support

Add money to your Apple Account balance - Apple Support

Check your Apple Account balance - Apple Support

How to redeem your Apple Gift Card or App Store & iTunes gift card - Apple Support

If your payment method is declined in the App Store or iTunes Store - Apple Support

Remember that this is a community of end users like you, and not Apple. We have no access to your accounts. Urquhart1244 has provided links to six (6) Apple help documents you can click or tap. Have you tried those?

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