iPhone is set to Central time (Chicago). Automatic is OFF. iPhone changes time zone to Eastern (New York) anyway.

I live in the Central time zone, near Chicago. My iPhone would switch between Central time and Eastern time several times per day, so I've turned AUTOMATIC off and manually selected Chicago. Now it switches daily. I have to open Settings and switch it from New York to Chicago again. This problem makes my phone unreliable for any scheduling because it switches without warning.

How can I set my iPhone to Central time and have it STICK? It does not need to change EVER.

Solutions I have tried:

Setting the phone to AUTOMATIC results in the time zone switching multiple times per day.

Setting the phone manually to Central time (Chicago) results in the phone switching to Eastern (New York) daily or every other day, randomly, without warning.

Moving to New York is not a solution.