You can manage your subscription after subscribing to free 7-day trial. The 7-day trial only offer annual pack at the moment but you can immediately change this to auto-renew to monthly by following the instructions below:
- Go to Settings > [your name] > iTunes & App Store.
- Tap your Apple ID at the top of the screen, then tap View Apple ID. You might need to sign in with your Apple ID.
- Scroll to Subscriptions, then tap it.
- Tap the subscription that you want to manage. If you're being charged for a subscription, but you don't see it in your list of subscriptions, it might be billed through someone other than Apple. Learn what to do if you still can’t view your subscription.
- Use the options to manage your subscription. You can choose a different subscription offering, or tap Cancel Subscription to cancel your subscription. If you cancel, your subscription will stop at the end of the current billing cycle.
Learn more about Insight Timer's Billing.