Welcome, I am Cory.
Please sign into your Kindle account at amazon.com
Once you sign in, please go to the payment management page here. - https://www.amazon.com/gp/digital/fiona/payment-settings
Once you go there, you will be able to enter the new billing information and remove your old billing information.
I hope I have answered your question today.
If you do not have anymore questions, please remember to rate my answer, so I get credit for assisting you today.