A subscription is cancelled when the user opts-out from the auto-renewal. Unlike in the case of Subscription Churn, the user will continue to use your app's paid features until the end of the current subscription period.
Apple/Google will let you know about the refunds via server2server notifications. Handle, store, and process them to build custom views with the cancelled subscriptions analytics.
Adapty does everything for you automatically. Simply install the SDK for your platform, open the Advanced dashboard and you'll see all the details!