To start a subscription with Sleepiest+ you first have to choose your trial/subscription type and then confirm with Apple the terms of your trial/subscription.
This is not something that is automatically opted into on launching the app and can't usually be done by mistake.
If you are unsure of if you are in a subscription please follow the steps below:
Open the Settings app.
Tap your name.
Tap Subscriptions. (If you don't see "Subscriptions", tap "iTunes & App Store" instead. Then tap your Apple ID, tap View Apple ID, sign in, scroll down to Subscriptions and tap Subscriptions.)
Tap the subscription that you want to manage.
Tap Cancel Subscription. If you don’t see Cancel Subscription, the subscription is already cancelled and won't renew.
Sleepiest has a free version, if you do not wish to pay you are still a valued member of the Sleepiest community and we give away a generous amount of content free of charge. Please do take advantage of this.