Can't add my Visa card

There are several ways to change you payment method, including on your computer, or iOS device, or also through the web browser. Attached here is a linked support article: https://support.apple.com/en-us/HT201266

If you want to change your payment type, you still need to go in through the App Store app, as outlined in the support article instructions.

Set up your Apple ID payment method and shipping address on Mac https://support.apple.com/guide/mac-help/set-apple-payment-method-shipping-address-mac-mchl29cac995/mac

On iPhone: Settings > Name > Payment & Shipping

What happens when you try? Error message(s)? Payment method declined?

Apple ID payment information - If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store.    

If necessary, contact iTunes Support. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call       

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.