On the rare chance you start getting calls from a nutter, you can take more serious steps. But really, that's something that has a vanishingly low probability of occurring, and if it does, the solution is fairly simple (get a new number). I choose not to plan my life around low-risk, low-probability threats.
A new number is a "simple" solution in your world? Because it would not be for at all! My number is on my resume, its attached to my credit cards and bank accounts, its the alternate contact for my Facebook account, my Dr's have it, friends and family across the country - including being the "out of area contact number" for my family in San Francisco in the event the big earthquake comes - etc. I trust those sources to have my number, but I'd rather it didn't get itself too easily just randomly out there; I have an ex-boyfriend from 20 years ago who is probably not a threat at all, but who after I broke up with him did some low level stalking of me, tried to commit suicide and last I heard became a junkie - yeah I'd rather he not be able to go into a public library and pull up my number. I'm sure my number is searchable if someone really tried pretty hard, but at the moment its not super easily accessible and it is in no way a simple thing for me to change it - it would be days worth of work trying to remember and then contact every source that I want to have my number to have them change it.
Just because changing your number is "simple" doesn't mean it is "easy" or cheap.
Thirty-five years ago, it cost us $40 to get a "new number" because we'd had one too many threatening phone calls from people trying to find the wacko who previously had that number. It might have been a "simple" solution - but I still had to pay for the change to the phone company and update ALL the family, friends, and businesses that needed to contact us with the new number (both of us were active duty military - so there were several offices to be contacted on base).
It took a couple of weeks to get MOST of them the new information and a couple of the cousins who lived further away missed connecting with us when they drove or made airline connections through Phoenix, Arizona on trips because they hadn't updated the little address book that they took with them (I suppose they updated the large address book at home - remember - this was before cell phones or even PDAs - back when you carried a physical paper phone number list with you or memorized the numbers).
I don't pass out my cell phone number for a second reason. We don't have texting on our plan (VorGuy picked our plan, not me). It costs money to get or send a text. I don't want to explain to him why I am getting texts from strangers who are trying to arrange something from Craigslist or Freecycle - some of them will punch in the number & send a text before reading the rest of the sentence - which reads "#123-456-7890 - please do not text this number".
It would almost be easier to lie and tell them that it is a landline and can't get texts than it would be to get them to read the instructions about not to try sending texts. But I digress...
Eight years ago, I was the membership chair for a group of (mostly) women, some elderly. We published a directory every year and the previous couple of editions had apparently not been pruned enough to suit the president of the board that year. I spent an extra six weeks calling everyone that I could, emailing everyone that I could, and asking for updated contact information by email, phone, and in person at the various meetings that I attended - when they picked up and dropped off their name tags or signed in as attending.
I got several people to update ONLY on my promise (and there was legal text in the directory requiring this) that it was ONLY for the organization to use for the organization - no spam, whether phone calls or emails. Again - legal language in document promising this.
Finally got it to the printer over a month late - but it was the most accurate one in years with up-to-date names, addresses, phone numbers, and added cell phone numbers & email addresses.
The vice president promptly sent out a mass emailing about some personal business endeavor of hers...against all the rules for the use of the data and promises made by the organization and its "parent" organization.
It made a few people mad.
What made me mad was that the next year, she was elected president (usual progression for a vice president) even though a number of people voted for someone else, she still had the "most" votes. I was NOT a happy person and neither were some of the ladies who remember getting that email.
It's been seven years since we moved away from that location - but I still wonder how she got away with it and then got "rewarded" because no one remembered her legal and etiquette blunder (using the email addresses and phone numbers for personal use instead of organizational purposes).