If you can't change your payment method in the App Store or iTunes Store
On June 30, 2018, Apple will implement changes to continue to ensure your financial data is protected when you make purchases on the iTunes Store or App Store. As a result of the changes, you will no longer be able to change your Apple ID payment information from devices using the following versions of Apple software:
● iOS 4.3.5 or earlier
● macOS 10.8.5 or earlier
● Apple TV Software 4.4.4 or earlier
You can learn how to change or remove your Apple ID payment information at the link below...