It seems the crux of the issue is that you said it constantly shows up. The only time you should ever see it is when you click the time in the menu bar, or the keyboard shortcut by holding the Function Key and the "n" button, where it will toggle the notification center on/off.
So are you inadvertently clicking the time or is it randomly appearing for no reason? If it is randomly appearing that would indicate there is some third party software installed that is causing the problem or possibly a custom keyboard shortcut that is being used. That is why I asked about Bartender, as that one has been seen to randomly choose a menu item.
While you cannot get rid of Notification Center, you also should not be seeing it, unless you do one of those actions to open it. I don't know if it is a keyboard shortcut in your case, third party software, or inadvertently clicking the time in the menu bar. If you rule out the keyboard shortcut and clicking the time, then post the free EtreCheck report to identify if there is any third party process running on your computer that could be causing that problem. The report contains no personal information.
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