If you are living in interior areas then you must have noticed that your Lumia device automatically switches to 2G network even if you have selected 3G in Mobile Operator settings. Before the Amber Update, their was a hidden setting named "Field Test" that allowed users to force 3G on their device. But in Amber Update Nokia removed it from the device. I have found a way to force 3G on your device using Field Test, but it will require Dev Unlock. If you are not familiar with it, better check out the our full tutorial to unlock your device. Check the video Here.
After unlocking follow these steps:
- Download a patched XAP file from Here.
- Now open Application Deployment, Select 'Device' in Target, Browse the XAP file you just downloaded and click 'Deploy'. Success.
- Now there will be an application called Native Toast Notification Launcher in you WP8 phone.
- Open the app(delete the text written) and copy paste the following: app://2377fe1b-c10f-47da-92f3-fc517345a3c0/_default#/Launcher;component/MainPage.xaml?DialString=3282
- Click Launch Toast.
- Click on the notification 'Toast Launcher Click me'
- Field Test Menu will appear. Click accept.
- Click Menu button (Three dots) - > Setting - > Network Mode - > 3G Only
- Enjoy (NOTE: Whenever you switch off your phone, repeat above steps(No need to unlock again).
XAP App Source: xda-developers
Note: We will not be responsible for any damage done on your device. Do this at your own risk.