Payment method could not be complete

We are not Apple but other end usrs like you. Allwe can do is point out Apple Support article on the subject. Please start here:

Add a payment method to your Apple ID - Apple Support

There ara also support option near the bottom of this Apple page:

Subscriptions and Billing - Official Apple Support

I wanted to set up my payment method on apple store because i have problem with my Apple ID when I wanted to download from the Apple store (ID has not been used on itunes Store) and I was trying to setup Payment and Bailing method but my payment method was not successful. Please what can I do. Thanks