Another unknown caller I suggest not to answer.  

Calls often then stops for a while, then starts up again.  Never leaves a message.

I'll bet it may be same as other numbers we don't know, pretending to sell discounted electric, telling us we've won a cruise / trip, that our car insurance expired, etc.  No wait, they might be from the make believe children's cancer society who keeps the money for themselves.  Take your pick, a scam is a scam, and an unwanted caller who doesn't stop calling is a ...

Liar liar, pants on fire, I won't believe anything they say if they ever do leave a message..  

Wish these people would get a real job instead of annoying half of the country with their bull phone calls.  

Guessing if someone works for one of these phony companies they have the same lack of morals as any common thief who doesn't care that they steal for a living.