Windows 10 Update finally available for Lumia 1520 on AT&T
The official Windows 10 Update released for the AT&T’s Lumia 1520
Months after the global roll out in March, the former flagship for AT&T is finally receiving the official Windows 10 Update. To update your Nokia Lumia 1520 to Windows 10 Mobile, you need to install the Upgrade Advisor app, and then go to Settings → Updates & Security to scan for an update.
After you upgrade your device from Windows Phone 8.1 to Windows 10 Mobile you will find that it runs one of the earlier builds (10586.1xx), but another phone update will bring the phone to the latest official version available to everyone on Windows 10 Mobile.