I have also been receiving this annoyance. When I attempt to call them back it, I get digital sounds like I am calling a fax machine. Also, I tried to contact the Annoyance Call Bureau (1-800-582-0655) listed above and found that these calls are legal. Not knowing where else to turn I went to Google, and found a Do Not Call Registry (
https://www.donotcall.gov/). Here I was able to register my phone number so this will not happen in the future. Next step is to contact the owner of the phone number in writing if I can find out for sure who it belong to and let them know I have registered, and to please remove my number from their list. Hope this helps.