How to subscribe JusTalk in-app purchase?
If you'd like to cancel your subscription:
1. Launch the Settings app.
2. Tap iTunes & App Store.
3. Tap on your Apple ID.
4. Tap View Apple ID when the pop up window appears.
5. Enter your Apple ID password or fingerprint ID when prompted.
6. Tap Subscriptions.
7. Tap the Subscription you want to cancel.
8. Tap Cancel Subscription.
9. Tap Confirm when prompted to confirm that you want to cancel your subscription.