I've been using nomorobo.com for several years now. if the phone only rings once, it was a robo call that was disconnected. Free for landline and something like $2 a month for mobile. I love it on the landline.
When I switched from Verizon to Optimum for my landline service last November, I was able to use nomorobo and it blocks most but not all of the garbage calls which come in on that line.
But my cell phone is another story. I have had the number for only 2 1/2 years, but about 90% of the calls I get on it are garbage calls. I pay about 11 cents per minute, so it adds up over time, especially if I have to retrieve a voice mail message and clear it out. Some of the garbage calls go right to voice mail (how?) and my phone never rings.
Another problem I have had with the cell phone is that I get a bunch of calls for the former owner of the phone number, asking for him by name. Often it was only the first name, so it took me nearly 2 years just to get his last name. When I found someone local with that name (a doctor), and I called his office, I was told by his staff that he never had my cell number (so it's another guy with the same name).
On the cell phone more than the land line, I get lots of calls from spoofed numbers, numbers with my area code and 3-digit exchange. And it's always the same bunch of robocalls, like the resort rewards or payday loans. I have asked this before but I'll ask it again - what kind of business model calls the same people over and over and over, knowing that they don't want to be called (re: the useless do not call list), just to annoy them while wasting everyone's time trying to sell them something they have no interest in? What is so hard about NOT calling people who do NOT want to be called?
I go to
http://800notes.com/ a lot to see if others have gotten garbage calls from the same number, and those spoofed (local) numbers never have anyone else posting about them.