Subscription is Cancelled when a user opt-out from auto-renewal. Unlike Subscription Churn, a user will continue to use your app's paid features until the end of a current subscription period.
When a user in an auto-renew off status you still have a chance for Restoring Subscription. Try Adapty's win-back campaigns: as soon as a user Cancels a Subscription, send promotional push notifications with a sweet discount. At least, you can get something.
Apple/Google will let you know about Refunds via server2server notifications. Handle, store and process them to build custom views with Cancelled Subscriptions analytics.
Adapty does everything for you automatically. Simple install SDK for your platform, open Advanced Dashboard and you're ready to go!