How does a customer cancel a subscription?

Desktop 

Within the account, navigate to the subscription details. Scroll to the bottom of the page and click the Cancel Subscription button. 

A form will appear. Along with a list of reasons for cancelling, the user will have an area to add additional comments. There are also buttons to Delay Shipment or Edit Products instead of cancelling. Once the user chooses an option from the list of reasons for cancelling, the Cancel Subscriptions button will be active.