Device unlock app is a special way of removing a network blockade from your phone.
There are currently three major networks that use this app. The first one who introduced this app is T-Mobile USA, after that the app came to Metro Pcs and finally AT&T has included the app as well.
The app is pre-installed on all supported devices and is very easy to use.
At the begging the app could be downloaded from Google shop, however it is no longer available in the shop.
The app should appear on the screen as soon as you insert an unaccepted simcard (from a different network).
If it doesn't show after that, you can find it My apps & games and than installed.
After the device is unlocked the app will delete itself automaticly so you don't need to worry about it.
The app gives you two options for unlocking.
Temporary unlock which lasts for a short time and permanent unlock which unlocks your device and never locks it again.
In order to unlock the device permanently, your device cannot be reported as lost or stolen, have any unpaid bills or be on contract.
However if you bought a used device that has any of these issues you can contact SIM-UNLOCK.NET to help you unlock this app.