If you downloaded the game through the Google Play Store, you can proceed with the settings yourself to prevent unintentional product sales in Google Play Store.

■ How to set a Google Play payment password
1. After running the Google play store, touch your profile picture on the right side of the search bar
2. Click on the Settings → User Controls → Select Require Authentication for Purchase
3. Select 'Authentication for every purchase through Google Play on this device'.
4. Set a payment password for your Google account