I teed off ATT and Comcast and so one of them put this really nasty high tech debt collector on me.  They use several numbers, I know each time I block one another calls me.  But all start with 408-42X-XXXX.  What they are doing is illegal, of course, but they don't care when you get them angry.  They just ]want to annoy you.  Fortunately, Google Voice helps me block, scren, and do-not-disturb these calls into silence.

Also uses (408) 427-2117, (408) 427-1424, (408) 427-1122, (408) 421-2301, (408) 421-2150, sometime 3x a day in combination.  Once someone identified themselves as Mike and asked for me by name.