Go to your device's Settings, then:
1. Scroll down and tap "iTunes & App Store";
2. Tap your "Apple ID";
3. Tap "View Apple ID";
4. Tap "Subscriptions"
5. Tap "Chamy";
6. Tap "Cancel subscription".
7. More information can be found here: https://support.apple.com/en-us/HT202039
Please note, you can continue using our free version after cancelling subscription.