It is very easy to update the details related to your shave plan, whether you have a new payment card or have moved.
Log into your Cornerstone account and go to the "Contact & delivery details" section.
There you can update your payment details, your login details (both the email used for your account as well as your password) and your delivery details (under the "Contact details" tab).
Be sure to click "Save changes" and "Confirm update" so that your updates successfully go through. And if you are making more than one change to your shave plan, please refresh the page after each update.