You can cancel your account at any time within your billing section. Simply click on "Cancel Your Subscription".
Your account will remain active until the end of the billing cycle, and you are able to resubscribe at any point afterward and retain your existing data (expired accounts will be purged after 6 months).
Cancellations can happen only through the 'admin' or 'master' account.
Hence, make sure that you are logged in in any of these accounts to cancel your subscription.