You will have to cancel your Daily Bodyweight Workout App subscription via iTunes.

To do so, please follow these instructions:

On the Home screen, tap Settings.
1. Tap iTunes & App Store.
2. Tap your Apple ID.
3. Tap View Apple ID. You might need to sign in.
4. Under Subscriptions, tap Manage.
5. If you don't see a subscription in iTunes and are still being charged, make sure that you're signed in with the correct Apple ID.
6. Tap the subscription that you want to manage.
7. Use the options to manage your subscription. You can choose a different subscription period, or turn off Automatic Renewal.
8. Turn off Automatic Renewal to cancel a subscription. Your subscription will stop at the end of the current billing cycle.