How To Stop iOS OTA Update Once Started on iPhone or iPad

If you start an iOS over-the-air update, that is, a update straight from your iPhone or iPad, from Settings > Software Update, and then need to stop the update before it's done downloading - follow these steps: 

1. Open "Settings" app.  

2. Tap "General." 

3. Tap "Storage & iCloud Usage." 

4. Under Storage heading, tap "Manage Storage."  

5. A list will populate. Find "iOS X.X" on the list, and tap on it. 

6. Now, tap "Delete Update", then again on the pop-up menu to confirm. 

7. To re-download the update, go back to Settings > General > Software Update.