If you wish to change your Billing Contact information or address then you can do this via the Billing page.
Navigate to -> Billing -> Billing & Payments
Here you will be presented with all your Billing and Payment options.
Fig 1 - Billing & Payment options
Changing your Billing Contact
Select the option: Billing Account Information and select your current contact, the screen will display all your current Billing Contact information, click in the relevant field and amend where required and press [Update]
Fig 2 - Billing Contact Details
Changing your Billing Address
Select the option: Billing Address and select your current details, the screen will display your current Billing Address, click in the relevant field and amend where required and press [Update]
Fig 3 - Billing Address