cancel iOS update while it's downloading

While its downloading, go to General>Settings>Usage>Manage Storage and the iOS update should appear among the list, and you just tap on that and press delete and when you go back to the 'Software Update' tab it will be back to 'Download and Install'

At the risk of bricking my iPhone, what I did to cancel the update and return to the initial "Download and Install" screen of the Software Update, I first did a hard reset then went back to settings>General>Software Update and it hang on Checking for Updates. Perhaps if I had of waited it would of returned to the initial state but I powered it off anyway, then back in the Software Update it checked for updates and returned with the "download and Install". It could of hang after the hard reset because right about now there will be several million people downloading IOS 8.

Like I said, hard resetting, powering off etc while updating is risky business and I only did it because it was a calculated risk i.e. there was a risk of bricking the device going ahead with the update as the progress was fluctuating from 51 to 63% and the settings app kept crashing, so I decided to quit it and use iTunes to update it.

Now it's time to get rid of the update on your iPhone or iPad. This will prevent iOS from throwing up the update alert at you every day:

1. Tap Settings.
2. Tap General.
3. Tap Storage & iCloud Usage.
4. Tap the first Manage Storage option (below "Storage" not "iCloud").
5. Locate the iOS update. It should be iOS followed by numbers, i.e., "iOS 9.3.2."
6. Tap Delete Update.
7. Tap Delete Update in the Delete Update alert window.

Turning off Automatic Updates and deleting the latest update from your Storage will prevent you from getting the alert windows in the future. Some users have reported that iOS re-downloads the update when the iPhone is connected to Wi-Fi

If the "Install Now" and "Remind Later" alert re-appears, check in your Storage & iCloud Usage and delete the update again.

You can turn off Wi-Fi to never see the update again, but we think this is slightly extreme.

You'll still get alerts from the App Store when Apple releases a new version. But these only come along every few months; not daily.

Hmmm...that's odd...well, the option is to just not install it once it's completed. It will take up that space on your device though when completed.

That is how you stop it by turning off Wi-Fi. It will not resume until you tell it to.

You saved my life !

TThanks for the info