Smart Network Switch is a feature on Android phones that allows your phone to automatically switch between WiFi and the mobile network. This allows the phone to maintain a high level of internet connectivity if your WiFi connection is too slow to provide a good user experience.
While this can provide a better internet experience, it can mean that you use more of your included data allowance. It is set to off by default, but if you want to turn it on (or want to turn it off if you have turned it on) follow these steps:
1. From the home screen, tap the “Apps” icon 2. Tap “Settings” 3. Tap “Wi-Fi”
4. Tap “MORE” 5. Tap “Smart network switch”
6. Tap “Off” to disable or “On” to enable
Click here for more information on how to manage your usage.