my iphone x on ios 11.2.1 automatically reverts time One ro 'aet automatically' every night!

I don't want my iPhone to control the time zone - it completely messes up my calendar and my head. I want it to stay at to my home zone.

So I go to send and deselect 'set time zone automatically'. And *every flicking night* it decides it knows better and switches the option back on! I've missed one meeting and one other alarm already because I had manually calculated it for the time zone and my iPhone jumped ahead missing the alarm. What the what??

This is clearly a big, isn't it?!