Subscriptions are managed through the App Store, not inside the app.
On iPhone / iPad:
Go to Settings → [Your Name] → Subscriptions → LevelPro → Cancel Subscription
Visit reportaproblem.apple.com, sign in with your Apple ID, find the LevelPro purchase and request a refund.
Go to Settings → [Your Name] → Subscriptions → LevelPro and select a different plan.
Make sure you are signed in with the same Apple ID used for the purchase. In the app, tap “Restore Purchases”.
All receipts are sent by Apple to the email associated with your Apple ID. You can view them at reportaproblem.apple.com.
LevelPro does not require a separate account. To remove all data, simply cancel your subscription through Apple Settings.