Unfortunately, samsung has removed the option to hide the notch after the one ui 3.0/3.1 update. You will have to get used to the notch. You can try using the developer options to see if there are any options to hide the camera cutout (notch) or add new styles to the camera cutout (notch).
To go to the developer options, follow this steps:
Go to settings > about phone > software information > tap Build Number 7 times or until you see the "You are a developer!" message. Then the developer mode will be unlocked. (I don't recommend trying this method since it could dissappear or get disabled after a software update)
