To cancel a subscription you must cancel the subscription and delete the account at the same time, this is to disconnect all of your mailboxes and remove all of your workspaces.
You must be the account owner to do this.
Important
Once you have done this, it cannot be reversed so please make sure you are certain before cancelling your subscription.
The Steps
Go to Settings > Billing Information > Scroll to the bottom of the page and click 'Delete Account & Cancel Subscription' as shown below.
