TLDR: What are the risks, consequences, of giving my phone number to civilian people I meet while socializing/dating or in casual life? If a bad actor gets my phone number, what attacks to expect, and how can protect myself from their attacks?
Disclaimer: I'm a super beginner in security as you'll easily find out by reading below. This is a question from a casual person, with the goal of informing casual, non-expert people like me, that I think, for example, a great chunk of women have while hesitating to give phone numbers to men they like but aren't sure they are violent/going to use phone number to do violent oppressive acts. In my experience people hesitate to give their phone numbers in my country, I want to know how unsafe this really is, and what is the solution.
So, I want to date people, to give my numbers to them, or to friends, I met casually in the street / outside, and, analogously, I'm worried THEY are worried/freaking out UNJUSTIFIEDLY about giving their phone number to me. I have researched about the posssible dangers of giving your number, and they don't scare me very much, except possibly the 2 factor authentication, for which the solution is to not have 2-factor authentication with a phone number to start with..
The problem of getting harassed/stalked requires the harasser to change numbers, which I would like if you answer me if they manage to do that or are stopped by the phone company, of course depends on company and country. In case they do, they can't avoid spending money calling me, while I just hang up if I don't hear a familiar hello. I don't see any scenario where this calls lead to me being in more danger than without the calls, the calls themselves just make my phone ring, how could that more than annoy me?
Also, if giving our phones number were that dangerous, then it's extremely in dissonance of how 99.9% conduct themselves in real life. Surely 99% has given their phone to friends, school were the kids go, the telephone directory, gym, dates... I mean, if start today not giving my phone number, that doesn't erase the already hundreds of entities I have shared my number with. So, if I already shared my number with others, maybe now it's on a call-spammer list and people can buy it online. Also, giving phone number can be bad for identity theft.
If giving phone number is dangerous, because of reasons I'm overlooking, is a solution to that to give email such as gmail? Because then, to spam you they would need to surpass google spam filter which is remarkably hard.