Changed your mind about the free trial? That is fine. Cancel before it ends and you will not be charged.
How the trial works
The trial lasts 7 days and comes with the yearly and monthly plans, when your Apple Account is eligible. Pay-As-You-Go and Lifetime start right away, with no trial.
The trial is offered once per Apple Account, so reinstalling the app will not bring it back.
If notifications are on, Wakeout sends you a heads-up on day 5, with two days left.
If you do nothing, your plan starts when the 7 days end. If you cancel before then, you are not charged, and you keep Wakeout for the rest of your trial.
To cancel the trial
In Wakeout, open Settings and tap "manage subscription". (Or open the App Store, tap your profile picture in the top right, then Subscriptions.)
Tap Wakeout.
Tap Cancel Free Trial (or Cancel Subscription) and confirm.
If you do not see Wakeout in the list, there is no active trial on this Apple Account. Check you are signed in with the Apple Account you used to start it. More on Apple's side: Apple Support.
See How does the free trial work for the full timeline.