iPhone 6 and 6+ users: Here's how to revert back to iOS 8 and regain Cellular Network
Instructions to revert back to iOS 8 for iPhone 6 and 6+
Download
iPhone 6+ - http://appldnld.apple.com/iOS8/031-05555.20140917.YWW0v/iPhone7,1_8.0_12A366_Res tore.ipsw
iPhone 6 - http://appldnld.apple.com/iOS8/031-05647.20140917.b0n9s/iPhone7,2_8.0_12A365_Res tore.ipsw
Download may take a while as everyone is downloading it right now
Once downloaded, move the file to the desktop (or wherever, just makes it easier to find)
Open iTunes
Connect iPhone to Computer
On Mac- while holding alt/option click on "check for updates". Finder will open up, navigate to the desktop and click on the ipsw file and follow the promptings. Takes 2-3 minutes with one reboot.
iPhone 6, iOS 8