Just for future reference, when that notification shows on the settings icon, it means your device has already downloaded the update file. You can get rid of the app badge by going into settings>general>iPhone storage. Somewhere in the list will be a software update file, usually several gb’s in size. Just tap on it and then tap on the delete option. With the file deleted, the app badge should disappear as well. However, as long as you have the “automatically install updates” option disabled, your device shouldn’t install it without your confirmation. I think, though I may be wrong, that once you delete the file, your device won’t redownload it, but it will download the next update to be released in the future.
For a more permanent solution, open iCleaner and tap on the + icon on the bottom left of the screen to access the advanced options menu. The first heading is Launch Daemons. Tap on that and scroll down to “OTA update daemons” and toggle the switch to the off position. I recommend leaving all the other settings alone unless you thoroughly understand what they are but disabling the OTA daemon is pretty safe. It just prevents your device from checking for and downloading future updates.
