How can I stop an iPod from upgrading the iOS once it has already started the download? I accidentally clicked to upgrade from iOS 7 to iOS 8.1.1. The problem is, I am a developer and want my device to remain at iOS 7 so I'm testing with the same OS and browser version that my corporate users are using in the field. However, there is no "Cancel" button (seriously, Apple? ...seriously? )

I tried shutting the device off and turning it back on, but it resumes the download after it's restarted. Same with turning WiFi on and off. I need to stop it permanently.

I read this macworld.com article that discusses how to revert back once you've upgraded, but at the top it specifies that it no longer works: "Update: The technique outlined here for reverting to iOS 7 no longer works as Apple has stopped signing versions of iOS prior to iOS 8."

I did read one "hacky" way to prevent the download from completing by leaving the video recorder on so space fills up and it can't finish. Is there a better way to do it?

(Hopefully this question is in the right place w/right tags - I haven't posted in this SE before)
Turn off wifi.  Reset All settings.  Phone reboots and download is canceled.