Cancellation is not done from inside the admin panel - there is no cancel button on Settings > Billing (an in-progress "cancel" icon exists in the underlying code for subscription add-ons, but it isn't wired up to anything in the current version). Follow the help-center article How do I cancel my subscription and contact Sprwt support; they process the cancellation on the billing account. Before cancelling, download any invoices you need from the Charges table and export your data (orders, customers, payments CSV), because access to the admin ends with the subscription.