This URL is the cancellation page — you do not have to hunt through settings
Go to the Google Play subscriptions cancellation page
https://play.google.com/store/account/subscriptions
Cancelling does not cut you off immediately. You keep access until the end of the period you already paid for, so if you have decided not to renew you can cancel straight away without losing anything.
This page covers every subscription bought inside an Android app. Anything you subscribed to on an iPhone has to be cancelled in the App Store instead.
Periods already billed are generally not refunded — cancelling only stops the next charge.
Prepaid plans (a one-off block of time) can have the unused part refunded separately; that is a different request from cancelling.
People who forget to cancel are not careless — the moment you decide and the moment you are charged are a whole month apart. Add LapseWatch on LINE and send “Google Play subscriptions 12/25” to record it. No install, no signup.
Want to see the whole picture? Add up a year of subscriptions (in Traditional Chinese); if you work at a computer there is also a Chrome extension that keeps everything on your own machine.
Interfaces change. Always treat the official page as the final word.