How do I cancel my Node/Subscription?

From Usage & Billing > Plans select 'Cancel Subscription'

Note: When your subscription is cancelled inside a current billing cycle, your subscription remains active until end of the current paid cycle.

Because subscription costs are paid forward, by extension mid-cycle account changes (i.e. cancel or downgrade) become effective at the end of the billing cycle.

Immediate cancellations are available through Billing Support: Submit a Request