You can change that info on your computer by going to the Amzon.com web site and then sign in.
To change your credit card information (such as the expiration date), you do so on Amazon.com. Go to https://www.amazon.com/gp/css/account/cards/view.html and then change your credit card information.
This sounds like you may be in the wrong area on the account page.
Are you on a computer now?
If yes, I can correct the issue for you with a Secure Remote Screen connect session. I will send you the information for this process.