They keep trying to get through to us, but it never works. My guess is they're using a robo-dialer, and said dialer does not like the 'Out of Service (SIT) tone sequence our Asterisk system sends (same thing the old 'Telezapper' did) when it first answers. The dialer's probably hanging up on its own.
Some Googling turned up a possible lead on these slime-suckers at this link.
They called and said they were verifying information for a business - they had an old address so I updated it. Then they rattled off a whole bunch of stuff I could not understand and said they would send a welcome packet in the mail. I asked for what and they repeated and said they were just verifying information, but they had asked if I was over 18 and I said yes to that. Sounded fishy so I told them again that I was not authorized to accept anything and hung up. They did tell me a phone number and New York address to cancel during the long rattling of info and I wrote the phone number down: 1-855-873-8363. If anything shows up on a phone bill or otherwise, we will take action.