Thanks for the question. I understand you are having issues with payment information. In my experience, this usually occurs due to two common reasons:
If your account information does not match your credit card, you may get a message stating "The credit card was declined."
To expand on the above, your billing name or address may not match the address listed on your credit card statement. Any discrepancy in punctuation, abbreviation, or capitalization can cause errors, which might prevent you from purchasing from the iTunes Store. If you moved, or if your zip code changed recently, ask your credit card company to make sure their records are up to date and match exactly what you are entering as your billing information.
The iTunes Store will place a minimal authorization hold on your credit card each time that you update your account information (equal to around 1 USD). The authorization hold is not a charge. The authorization hold is placed on your credit card to make sure that the information provided matches the information on file with your financial institution. The authorization hold will not be displayed in your iTunes Store purchase history.
If there are insufficient funds in the account to cover the authorization hold, you may experience issues with your credit card being declined.
For more information, see the following helpful resources: