Most users set tailored carrier plans for smartphones with which they can can navigate at top speeds until they consume a certain amount of data. Once the planned amount of data  is consumed, the speed is reduced or metered.
To keep a precise control of spent consumption  on our phone ,there are several applications, but one caught our attention because of its simplicity and efficiency, ideal to have everything under control at a glance. The application is called My Data Manager, and is free.
My Data Manager
Once installed, you need to configure it. To do this, you must let the program know the day when the operator starts to charge and the amount of data you have contracted. You can also set alarms and get notified when you have consumed a certain amount of data, so you’ll have everything under control. Besides that, My Data Manager creates a top of the most internet thirsty applications installed on your smartphone, and if one of them goes crazy over night or consumes data without letting you know, you’ll be informed and you will be able to uninstall it.
The control panel is able to differentiate between network types as 3G, WiFi or Roaming and you can set notification levels for each one of these categories.
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Control which apps use background data on Android Jelly Bean | Geena Lester's Tech Blog
[...] Bring up your Settings menu and you should find the Data usage app near the bottom of the Wireless and networks section (the section names may vary between devices). Tap on it and you’ll get taken to the main screen of the app, which is where the real fun begins. A smart app for this purpose is My Data Manager for Android 4.2 Jelly Bean. [...]