First thing (<i>before</i> the problem you're trying to address): There is a "do not call" registry. For reasons that I do not understand, (most) spammers respect it for our home phone, but not for cell phones. That thing needs to have teeth in it - like, sending-people-to-jail kinds of teeth. It's a travesty that spammers can just run all over that registry.<p>If that were in place, then the answer would be "put your number on the do not call list". But for whatever reason, that fix doesn't currently work.<p>On, then, to the problem you're trying to address. It needs to become illegal and/or technologically impossible to spoof caller ID <i>to a number that you don't own</i>. That is, if you're Apple, and you want all your outgoing calls to present as your main number, that's fine, because you own that number. But masquerading as a number you don't own? No way. It needs to be either impossible or illegal, preferably both.<p>But what about someone who's, for example, a whistleblower, and can't give out their number without blowing their identity? They could still <i>block</i> the number, but not <i>change</i> it. The caller ID shows up as "Unavailable" or "Blocked" (I just had one of those while making this comment, in fact.) The recipient can then decide to reject that call simply because of the lack of caller ID (as I in fact did).