I live in a house with 3 flats within it and mine has the thermostat. The other 2 tenants have my number so they can just text me if they're hot or cold or whatever, it's never been a problem. So I guess she knocks, I'm not home, so she lets herself in and adjusts the temperature and unplugs the dehumidifier.

I walk in and wonder why it's so hot, and see that she left me a note on the back of my door saying she 'took the liberty' to turn the heat up and unplug and empty my dehumidifier and that I don't need to use it as it's winter and the heat from the furnace will be sufficient.
Like...am I in the Twilight Zone? Am I overreacting?

You can't just go into someone's apartment. What should I do, ATRL?