I've been getting calls several times a day as well.  I tried to call back yesterday and it says the number is disconnected.  I answered today and the caller disconnected immediately.

if you don't know a number don't answer , see if they leave a message. Don't call them back cuz then they get your name on caller ID and know your name . If you do call back and hear the message that the numbers disconnected it's just a recording they copied from another phone line that's disconnected using it as an answering machine message so you think that. Just a bunch of crap. Plus they use magic jack and are not calling from where it says on caller ID probably from another country or state to try and scam you so beware! Legit companies don't hide and sometimes leave messages. My advice if you can block them do it and never hear from them again. Hope this helps out!