How do I change my credit card when ordering a book

You need to go to the Amazon web site. Select "Account & Lists," "Your Account," then "Payment Options" to update your credit card information.

For this one, i would recommend you to go check out https://privacy.com/ they offer virtual credit cards with different numbers that will resolve your issue. or you can click this link to redirect you to the website. Privacy Seamless Secure Online Card Payments

THE BEST WAY TO ADD A CREDIT CARD TO YOUR AMAZON ACCOUNT TO USE WITH YOUR KINDLE IS TO GO TO THE MAIN AMAZON.COM WEBSITE LOG IN AND GO TO MY ACCOUNT YOU WILL NEED TO FIND ADD A CREDIT CARD ...YOU CAN THEN ADD THE CREDIT CARD AND ALSO SET IT UP FOR ONE CLICK PURCHASES FOR YOUR BOOKS. MAKE SURE THAT YOUR KINDLE IS REGISTERED WITH AMAZON.COM THIS YOU SHOULD DO FIRST BEFORE ADDING YOUR CREDIT CARD. Amazon com Credit Cards Credit Payment Cards

set new credit card as default payment method

Go into your Amazon account and update your account info.

Verify that you activated the new card. Also, note that the new card will have a different three-digit security code than the old card did. Either of these issues will cause a refusal of the card.

Contact Kindle support. Fire Kindle Echo Support

You'd have to do it on your Kindle account, not on reader.

You need to change the number on the Amazon site. Go to Amazon, your account, Manage payment options, will probably ask you to verify log in info, Click on Add payment method, You MUST set new card as default. That may be what you missed. I did it the last time I changed mine. There should be an option to delete old numbers.