A lot of these calls come from people who are paid to do telephone solicitation.  They are compensated to some degree by the number of calls they are credited with making.  They call, you answer, they hang up.  They don't want to talk to you any more than you want to talk to them.  It's only pennies per call, but cha-ching!  They are ripping off their employers and being a P I T A to the rest of us.  Research the number, call the company and lodge a complaint.  Customer service being what it is though, it will probably and unfortunately, make no difference.