iPhone SE dims despite settings to the contrary

I have a new iPhone SE2020. About 10 times a day it dims itself for no reason PLEASE DON'T ANSWER UNTIL YOU READ THE FOLLOWING.

Under displays and Brightness I have the Automatic switch selected "OFF"

I have True Tone selected "OFF"

I have Night Shift selected "OFF"

Thanks in advance. But I keep asking the same question and keep getting told to turn off "Automatic." If I can't find an answer here I'm going to return the phone. Thanks in advance.

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