How do I get rid of that message?

If you have never had the device serviced by an unauthorized service provider, make an appointment at the Genius Bar of your local Apple Store. That's an indication that something has failed.

If you had the phone serviced by an unauthorized service provider, you can't get rid of the message. It's a warning that parts have been replace with non-Apple parts.

Make an appointment at the Apple Store or take the phone to an authorized Apple Service shop to let them run some checks and diagnose the issue.

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Hopefully, you did not have the camera replaced, which would indicate that the wrong part was installed.