this might be "Vishing", while not the actual calling number, for some reason they troll phone numbers looking for ones that will answer then hang up, then they troll online databases they know about and try to locate info on your number that they can then call you back under false pretenses & con you into giving out sensitive banking information so they can rip you off
Thanks, now I do not feel so bad about not answering this number, which shows up 2-3 times a day for a week now and has never left a message on my work line.