You can cancel a customer’s subscription by entering an expiration date in the customer’s subscription record.
Simply go to Customers, click the Customer's name, scroll down to Customer Subscriptions and click the Subscription record number.
Click the edit pencil next to the subscription record number, enter the expiration date, and click Finish.
Please note that eliminating subscription options from a product will have no impact on active, existing subscriptions. It will only prevent future subscriptions.