"...pretty much all cell phones have built-in number blocking capabilities."
I don't know what happens when you type your cell number into a search box, but mine pulls up my address, my children, my ex-husband, my first ex-husband, his second wife, her son, their daughter, my cousin's wife, and my mother, and that's just on the first page of contacts, along with the name of every city I've ever lived in, my most recent property tax bill, and that I'm single.
I used to routinely scrub my internet presence, but don't bother anymore because it's just all back up again in less than a month. The problem isn't that you can't block unwanted calls. The problem is that having your cell number pretty much means not much about you is unattainable.
Also, parenthetically, I just got reminded today that the sole advantage SLS used to have over Kik, which was the inability to send unsolicited dick pics, vanished with the end of mail. Now your eyes can get assaulted on the regular by some guy's ugly dick when you make the mistake of opening a message.