Robodialer.

Called and didn't answer as it said UNKNOWN CALLER.  Reported to be blocked.

sometimes we get 4 to 6 calls a day from this number and no one is on the line.

CID: Out of Area (although 562 is my area code)
Answered because I was expecting a business-related local call. Brief silence and then male caller asked for me by first name. He launched into a pitch, "Hi, I'm Michael the painter, and I work with my father, also a painter." I interrupted, said I'm a renter and furthermore that my number is on the Do Not Call list. He said, "OK, I'll put you on our Do Not Call list." Of course, he had no business calling me at all, as I've never used their services or those of any other local painters.