Some good news for Lumia 635 and HTC One for Windows owners on AT&T. It seems both the devices are now receiving Windows Phone 8.1 GDR2 update. The Windows Phone 8.1 GDR2 OS version for Lumia 635 is 8.10.15137.148.
You may like to read all the details about Windows Phone 8.1 update 2 aka GDR2 at our dedicated page.
Thanks Mike, Roku & many others for the tips. Cheers!!