Welcome, I am Cory.
I am sorry you are having a problem with this.
Please sign into your Kindle account at amazon.com
Once you sign in, please go to the payment management page here. -
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 I have not, please reply and let me know before you rate my answer.
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Are you able to login to you're account on Amazon.com?