The Cancel subscription modal explains that cancelling stops all future renewals but does not cancel upcoming orders already purchased, and lists the dates that will still be fulfilled. If cancel reasons are on, a reason (and justification when required) is mandatory. On confirmation the subscription is flagged cancelled, auto-renewal is turned off, you receive Admin: User Subscription Cancel, the customer receives Subscription: Cancel, and the action is written to the subscription's audit log as a customer cancellation. This is only possible when Show Cancel button on profile = Client can Cancel Subscription and the subscription's Cancellation rule is Self-service; with Request only the customer sends a request instead.