The scammers get lists because none of your information is private anymore and hasn't been for a long time.  Technology has enabled anyone who wants personal information to buy it.  Scammers and Telemarketers deal with the data mining industry that sell lists about anything and everything (age groups, ethnic groups, religious groups, political groups - you name it).  Just picking up the phone and answering indicates that yours is a live line and it gets put on a list to resell.

This is todays world.  Never answer calls you don't recognize.  Let them go to a recoder.  Never call back a number that doesn't leave a legitimate message.There are a million tricks these scum use.  Don't be taken in.

Go online and search for a call blocker that works with your service provider.