Hi, thanks for using JustAnswer.com I am Cris and will be glad to assist you with your issue.
Use the link I have provided below to update the credit card on your account. Log in with your Amazon account, once your in click on Settings, then Edit Payment Settings.
You can then update your credit card info.
Let me know if this solutions works for you. If it does please take the time to rate my service and submit at the top.