To cancel your PRO subscription simply follow these instructions:
For Android
- Go to your phone's Play Store > Click on the ≡ icon > Click Subscriptions.
- Tap the subscription that you want to manage.
- Cancel Subscription.
For iOS
- Go to your phone's Settings > Go to iTunes & App Store > Click on Apple ID and view it > Scroll down to Subscriptions.
- Tap the subscription that you want to manage.
- Choose a different subscription option, or tap Cancel Subscription.
For more information regarding subscriptions on iOS, you can follow this link.