How can I stop a pop-up notification from appearing on my phone?

Yes, sure, so you have to go to Settings on your phone. Once in Settings, you have to go to Apps Notifications. Once in Apps Notifications, go to See All Apps. On the top right of the screen, you'll see three dots. Press Restore Show System. Yes, press Show System. Once you press Show System, you have to look up for the option that's Door Speed. Once in Door Speed, it has to be on, and you have to press Open. All you have to do is just turn on the Messaging app and the Phone app, and that's it. Those are the only apps that can be restricted.