I don't know why, but Nomorobo stopped working for me. In the past month I've received several spam & scam calls per day: and they all ring through. I sent a list of the numbers, marked by Caller ID as "Suspected Spam", to tech support. All they could tell me was that the numbers hadn't been reported as spam and, therefore, weren't blocked.
Since I receive a lot of legitimate calls from unfamiliar numbers, I can't put the phone in lockdown and restrict it to my contacts. While I was presented with the option of Nomorobo Max, which screens every call in real time and only passes through the legitimate ones, it's $5/month instead of the $2 for basic.
I can do pretty much the same thing with Text Call, built into the phone, for free! I have to actively control it, but at least I'm not paying a subscription for something to do it for me (and every once in awhile, I feel like having fun by answering the calls and messing with them).
Text Call is pretty cool once it's set up, and a few custom responses are saved.