If you have a Active T-Mobile USA device and it's locked via the Unlock Application, this is the service you need to unlock it.
Please check your device prior to purchase, When you try to complete the unlock from the App menu is has to show "Unlock Failed: This mobile device is not eligible for unlock." message! If you see anything else do not buy as there is a issue with the phone.
Once the unlock request is Done, customer need to do:
Connect phone to*WiFi*
Go to Google play store and install Device Unlock app from T-Mobile.
Open app and select Permanent Unlock
Phone will check status from server and reboot, and will be unlocked !