an update…
Since April, I've been using AT&T Call Protect, the free version, not the $4/month version. I've been diligently reporting and blocking spammers, scammers, & telemarketers. At first, I was getting about 5 calls each day. Lately (mid July 2019) I've noticed that the unwanted calls has significantly dropped, to about 3 calls per week. The rest aren't blocked, but are identified as unwanted – AT&T Flagged. That's real progress. I hope it lasts.
The FCC has finally authorized cell phone service providers to atuomaticaly block spam calls, but didn't require them to do it for free. AT&T Call Protect will begin that sometime this fall. I don't know what they will charge.
In May, I dropped my landline phone. I replaced my old slower modem, which had VOIP, with a much faster modem. Modems cost much less without VOIP, so I dropped it. I haven't missed it at all.