Login to your account and follow the instruction below.
Click on the 'Manage Account' located at the bottom of the list on the left hand side of the page.
Click on the 'Cancel Subscription' tab and then Click on the 'Continue to billing portal' button.
You will then be taken to the Customer Portal page, as shown below.
In the Payment Method Section (3rd Section down the page) you will see and Edit link at the top-right.
Click on the Edit link and you will be redirected to the Change your plan page.
You will now be presented with the form you will use to change your details.
Change your details, double check them, just in case and then click Update.
If the process has been successful you will be redirected back to the Customer Portal and there should be a message in green at the top of the page “Successfully updated your credit card details”.
The message will disappear after 5 seconds.
If it process was unsuccessful please go back to and try again.