Begin be navigating to your Billing settings page.
Open the dropdown menu by clicking your profile picture, in the top right.
Select Settings
From Settings, select Billing via the left navbar
Select Manage next to the appropriate service
From this view, you're able to update and add payment methods as well as edit your billing information.
A history of invoices is also viewable here.
Note: A cancelled subscription will only reflect a downgrade of service at the end of the current billing cycle/subscription period.