The building's caretaker appeared to discuss the situation 5 minutes after OP disregarded the sign. I don't know that a phone number on the note would have changed anything.
I’m just saying, to the extent that there’s a moral question here, “how unreasonable was it for the author to ignore the sign?” I think it’s a lot more reasonable if there are no alternatives given.
My take on TFA was that the lesson was “adults negotiate with each other, have the confidence to reject offers, and the humility to respect when their own offers are rejected.” Quietly seething about something you’re not OK with is bad—you are responsible for representing your own interests, and expecting somebody else to anticipate your needs instead of expecting yourself to raise them is not responsible and not “adult”. Likewise, expect other people to represent their interests, and expect them to expect you to represent your interests.
Now, given that framing, I’m speaking to the question: was the author acting rightly (responsibly representing his own interests) or wrongly (disrespecting the building authorities’ “rejection” of his “offer” to rent the space, contingent AC control)? I say rightly, because he had no other way to represent his interests.
If there had been a number on the sign, turning the ac off instead of calling the number would have been wrong. OTOH, if the building engineer or whoever is mad that the numberless sign was ignored, well, obviously someone wanted it off (hence the sign), and you can’t expect that person to disappear. Maybe put a number on there and talk to them.
