Here are the steps to turn off auto-renewal for monthly subscriptions purchased through the JibJab mobile app:
1. Go to the Settings app on your phone
2. Tap [your name] and then iTunes & App Store.
3. Tap your Apple ID at the top of the screen.
4. Tap View Apple ID. You might need to authenticate your Apple ID.
5. Tap Subscriptions.
6. Tap JibJab from the menu
7. Tap Cancel Subscription to cancel your subscription. If you cancel, your subscription will stop at the end of the current billing cycle.
You can also view these instructions on Apple's help website here: https://support.apple.com/en-us/ht202039