Why is it asking for my payment method to purchase certain apps, but when I do add my card it says it’s already added on my acc??

Hello Cjm50,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. This article goes over how to update or change your payment method: If you need to change or update your Apple ID payment method - Apple Support

"If you need to change or update your Apple ID payment method

Learn how to edit the payment method that you use for subscriptions like iCloud+ and Apple Music, apps from the App Store, and other Apple media purchases.

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, add a new card first, then remove the old card.

Update your payment method on your 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.

Update your payment method on your Mac

1. Open the App Store.
2. Click your name or the Sign In button.
3. Click Account Settings.
4. Next to Payment Information, click Manage Payments. (If you're using an older version of macOS, click Edit next to Payment Type.)
5. Click Add Payment, then enter the new payment method. Click Done.

       6. Click Edit next to the old payment method, then click Remove Payment Method.

Update your payment method on your Windows PC or Microsoft Surface

1. Open iTunes.
2. In the menu bar at the top of the iTunes window, choose Account, then choose View My Account.
3. Choose Manage Payments. (If you're using an older version of iTunes, tap or click Edit next to Payment Type.)
4. Choose Add Payment. 
5. Enter your new payment method, then choose Done.

Learn more

• Moving to a new country or region? Learn how to change the country or region for your Apple ID.
• Need to edit Apple Pay information? Change or remove the payment cards that you use with Apple Pay.
• Learn what to do if you can't remove a payment method."

If you still need help with your account, please reach out to Apple's billing experts here: Get Support

We hope this helps.

Cheers!