How do I change my billing information when paying for the cloud practitioner exam?

Billing information is not stored in your profile. If you have not yet scheduled your exam, you can log in to https://kiku.aws.training/Certification, then click Register for an Exam. From there you can find which exam you want to register for in the list, then click Schedule with [provider of your choice]. Once you are directed to the provider's website, such as PearsonVue, that is where you are able to click through the options until you can click Proceed to Checkout. This is where you will provide the billing information for the purchase.

If your organization has provided you with a voucher, you can enter that on the Enter payment and billing screen, and pay for the remaining amount with a credit card.

If your company will be reimbursing you for a portion, you will pay here with a credit card in full and submit the receipt to your company to be reimbursed directly to you.

If you have already registered and paid for an upcoming certification, then you would have already been charged. To change that, you would need to cancel the exam and it will be refunded. Then schedule the exam with a new payment method. You are charged at the time of registration.