I leave a generic voicemail greeting; ANY unknown / unlisted Caller ID number talks to them IF they're legit. I only answer calls from sources I recognize. It doesn't bother me now if a scammer calls me; they hang up the second my voicemail goes on.
This particular number is a "decoy"; the actual source is located along the U.S / Canada border ( Canada side ), just above North Dakota. Yes folks, Canada has a "mafia"--and they don't mind spending the money on phone banks IF they can get huge lists of "marks" and sell those "hot lists" to other scumbag scammers.
Couple of months ago, FBI intercepted a scammer "hot list" of residences in affluent areas of California---that was being sold for $180,000!! One of the interested scumbag buyers was from Jamaica; shows you how big this "business" and problem is....and it's growing worse as our U.S. economy gets worse; sign of the times.