It won’t let me add a payment

Can you provide more details such as the exact wording of error messages when it says you cannot add it?

See this article about updating payment methods on various platforms (iPhone, Mac, etc.): If you need to change or update your Apple ID payment method - Apple Support

"If you change your address, the credit or debit card information that you use with your Apple ID might be automatically updated by your financial institution, and you don't need to take action. But if there's an issue [such as you having a subscription or being a Family Sharing Organizer], add a new card first, then remove the old card."

Here is how you update your payment method on an iPhone or iPad:

1. Open the Settings app.

2. Tap your name.

3. Tap Payment & Shipping. You might be asked to sign in with your Apple ID.

4. Tap Add Payment Method, enter the new payment method, then tap Done.

5. Tap Edit.

6. Tap the red delete button next to the old payment method, then tap Delete.

Read this document about how to view your current payment types and add Apple ID payment methods on an Apple mobile device, a Mac, or a PC --> Add a payment method to your Apple ID - Apple Support

If an item appears in red then it is no longer working and you either need to replace it or get it working again.

Check this resource about what to do if your payment method is declined in the App Store or iTunes Store. Click here --> If your payment method is declined in the App Store or iTunes Store - Apple Support

- Apple is checking with your financial institution if the payment method is valid and receiving 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 your payment method is up to date or to try a different one ( If you need to change or update your Apple ID payment method - Apple Support ).

- Make sure this is one of the payment methods that you can use with your account, as listed in this support article: Payment methods that you can use with your Apple ID - Apple Support . A solution may also be to use a method from the same country as the store you are using. It is frequently posted here that this is a requirement but the only official statement I can find about international payment methods is what Apple itself says is in its own support article specifically helping you with declined payment methods: If your payment method is declined in the App Store or iTunes Store - Apple Support : "You might need to ask your financial institution to allow international purchases on your debit or credit card". If Apple is requiring you to use a card from the same country, it certainly isn't clearly stating this in any of its documentation that I have seen (and yes, I read all the legal documents which is more than many people do).

・Unfortunately the payment methods list is somewhat general and does include individual brands of cards (I guess there are too many and are constantly changing).

・Also read any footnotes in the document.

・Finally, note that the document only says which methods _are_ acceptable. Apparently certain types (usually a credit or debit card) _must_ also be present under certain situations such as when a subscription is involved.

If you still have problems, contact official Apple Support. Click here --> Choose your country or region - Official Apple Support 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:

See a list of Apple phone numbers around the world, in this article --> Contact Apple for support and service - Apple Support

If you're in India, click on this link to read an April 2022 notice 'About billing for Apple subscriptions and media products in India' --> About billing for Apple subscriptions and media products in India - Apple Support

Additional verification that may be required when making purchases in Europe --> About billing and purchases in Europe - Apple Support

If an app or feature on your device is not working, not appearing, or is restricted (grayed out), it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support

Tap Settings > Screen Time > Content & Privacy > scroll to Allow Changes.

- If the device is managed (Settings > General > VPN & Device Management), contact the IT department that is doing the managing.

If you already tried (to no avail) all the steps provided in the suport article that led you here, I suggest that you contact iTunes Store Support Team directly, and explain your problem, using this specific link:--> https://getsupport.apple.com/?caller=ikb&PGF=PGF51002&category_id=SC0060&symptom_id=21084

(if you get no help, look at the bottom of the above link, where you can contact them using "chat" or "phone" options).

Regards

Giulio