Re: "App Store : Cannot verify payment information"
Apple support does have this article online:
If a message says 'billing problem with previous purchase' or 'verification required' - Apple Support
and
How Apple uses your payment information - Apple Support
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Re: "I am unable to add a new payment method. Why?"
Have you signed in (to your device) with your Apple ID: Sign in with your Apple ID - Apple Support
You may want to check the payment methods that Apple can accept in your country or region:
Payment methods that you can use with your Apple ID - Apple Support
You are asking Apple users, like yourself in this Community.
No-one here has access to your accounts or details.
For the info. you need, you may want to contact Apple Support
Eg: from this link: Official Apple Support or this webpage: Subscriptions and Billing - Official Apple Support
or
See a list of Apple phone numbers around the world
Contact Apple for support and service - Apple Support