Are you holding off on updating to iOS 12, and are tired of seeing the update notification on your iPhone XS/XR/XS Max? Worse, are you worried that you might accidentally tap on the update?
There are lots of reasons not to upgrade to iOS 12, especially if you have an older device. However, the constant nagging from Apple if you don't update your operating system can also get annoying after a while. Luckily, there is a way to get Apple to stop bothering you about it. Here is how to stop the iOS 12 update notification:
Turn Off Automatic Updates to Stop iOS 12 Update Notification
The first way to turn off the nagging update notification is to turn off automatic updates. Note that this method will only work for future updates, though. The reason you are getting nagged is because the update was already downloaded and iOS wants you to install it. (How to get rid of this downloaded update is explained in Method #2.)
At any rate, here are the steps to turn it off for future updates:
(1) On your iPhone, go to your Settings.
(2) Tap where it says iTunes & App Stores.
(3) Look where it says Automatic Downloads. Under that, you will see Updates. You can set the slider to the off position to turn off automatic updates.
Delete the iOS Update to Stop iOS 12 Update Notification
After following the first method above, you should no longer have to worry about automatic updates. However, you need to delete the current upgrade that already automatically installed itself. Here's how you do it:
(1) On your iPhone, go to Settings.
(2) Tap where it says General.
(3) Go to Storage & iCloud Usage.
(4) Tap Manage Storage (directly under Storage).
(5) Find the latest iOS update. It will look something like: "iOS 12."
(6) Hit Delete Update.
(7) A message will come up on the screen. Once again, tap where it says Delete Update to confirm.
Blocking Apple Software Update Domains on a Router/Gateway
In spite of all of this, it's still possible that the new iOS update will download itself if you are connected to WIFI. One way to prevent this from happening is to turn off your WIFI in Settings and just never use WIFI again.
This can be inconvenient, though, so instead you can just block the domains associated with Apple software updates on your router. Of course, this won't work when you're using WIFI outside of your house, but it's better than nothing.
(1) Go into your router's settings. This varies depending on the type of router you have, but usually you can access the settings by typing a certain address in your browser while connected to the router. Ask the router's manufacturer for more details.
(2) Find the area in the settings that allows you to block certain domains. Again, this varies depending on your router.
(3) Add appldnld.apple.com and mesu.apple.com to the block list.
This should make it impossible for your device to download updates through your WIFI network. Keep in mind, though, that this will prevent all devices that use this network from downloading Apple software updates.
Just Accept & Install Update to Stop iOS 12 Update Notification
Finally, you may find it extremely impractical to hide from the iOS 12 update. Since it will tend to want to install itself on your device, there will come a time when it will find a way. Maybe you'll accidentally use the WIFI at a cafe, or maybe the other people who live in your house will want to use the WIFI to update their own devices.
So you might just want to give up and install the update. Yes, iOS 12 is not for everyone. Maybe you have an older device and you find that the older iOS versions are faster. Maybe you're just used to your current iOS version and you don't want to deal with all of iOS 12's changes.
Change is inevitable, though. For security reasons and to simply keep up with the times, it might be worth it to just install iOS 12 and be done with it.
If you're interesting in iOS 12 or upgrading to it, you can find a complete guide on this new version of iOS from iOS 12 Upgrade Tips.
If you're tired of Apple constantly nagging you to upgrade to iOS 12, there are some ways to prevent the notification from coming up all the time. These methods are kind of temporary, though, since the only failsafe way to do this is to block Apple's software update servers from your WiFi router. Eventually, you will probably have to update.