Subscriptions bought in the app are managed by Apple, so you cancel them on your iPhone, not here.
- Open Settings on your iPhone.
- Tap your name, then Subscriptions.
- Tap Repcrow Pro, then Cancel Subscription.
You can also get there from the Repcrow Pro screen in the app: when Pro is active it shows a Manage subscription button.
Cancel at least 24 hours before the period ends to avoid the next charge. Pro keeps working until the end of the period you've paid for, and then the app goes back to the free features. Your workouts, history and recordings stay exactly where they are.