To cancel a subscription follow the steps below:

On your mobile device:

1. Launch Google Play Market;
2. Tap Menu button in upper left corner of the screen and select Account;
3. Open Subscriptions and find Business Card Reader;
4. Press "Cancel" button and tap "Yes" to confirm.

On your computer:

1. Open any web-browser and go to play.google.com/store/account;
2. Login using your Google-account;
3. Find the application in Subscriptions;
4. Click Cancel Subscription.

Important: uninstalling the application will not automatically stop purchased subscription. If you uninstall the application without cancelling subscription, you will still be charged.

More information could be found in the following article of Google Play Knowledge Base.