Follow these simple steps to Enable or Disable Data Network on your Android phone
1. Open "Setting" App
2. Go to "More Setting"
*On some devices with Ginger Bread ROM you might go to "Wireless and Networks"
3. Tap on "Mobile Networks"
4. Activate or Deactivate the "Mobile Data" option
Note that, If you are using a Samsung Galaxy device, you can simply hold the Power button and Enable or Disable this feature on the opened window