How to fix?

Review this document about what to do "If your payment method is declined in the App Store or iTunes Store" Click here --> https://support.apple.com/HT203005 It mostly just suggests you make sure your payment method is up to date or to try a different one. Apple is probably just checking with the system linking to your financial institution and asking if the payment method is valid. The system is providing a negative response. Make sure the name and address are entered exactly as it appears on your financial institution bills and that the 3 digit CVV is correct. Check with your financial institution about the status of your card.

Make sure this is one of the 'Payment methods that you can use with your Apple ID'; click here --> https://support.apple.com/HT202631 For most people this means a card from the same country as the store you are using, but read the part at the bottom of the support document for specifics. Also read any footnotes in the document for a payment method.

If you still have problems, contact official Apple Support. 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." - https://support.apple.com/HT201232

Click on this link to read an October 2021 notice 'About billing of subscriptions in India' --> https://support.apple.com/HT212781

Hi,

If you are getting an error message that the payment method cannot be used with the ITS, it means the card has been disallowed from future use, including the ability to add it to your Apple ID.

I would recommend confirming if you have previously disputed any charges with your bank from Apple.com/bill with that card, or if you have had unauthorized charges reported and/or refunded to that card.

This does not apply for purchases on Apple.com, ARS, or with Apple Pay.

You can also contact Apple Support to further confirm the reason it has been disallowed.

Hope this helps!