This URL is the cancellation page — you do not have to hunt through settings
Go to the Apple / App Store subscriptions cancellation page
https://apps.apple.com/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 app. If you subscribed to Netflix, Spotify or YouTube Premium on an iPhone, Apple is the one charging you — this is the only place to cancel, and you will not find a cancel button on the service's own website.
“I cannot find the subscription I want to cancel” usually means it is not billed through the App Store. Check Google Play or the service's own website.
The path on an iPhone is: Settings → (your name at the top) → Subscriptions.
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 “Apple / App Store 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.