There may be a way to cancel your subscription on the Xbox One, but I don't have access to mine at the moment. Probably go to your account from the dashboard and look for an option to view subscriptions.
You can also cancel it from the web by logging in to Microsoft's web site with the same account that has the Groove Music Pass tied to it...
● Sign in (top right)
● Click your name at top right and select "View Account"
● Click on the tab for "Services & Subscriptions"
● Groove Music should be on the list and there should be an option to cancel your subscription.