Yes it is VERY annoying!! I have been called several times a day with different numbers using the 313 prefix.What could possibly be their purpose if they keep calling and hanging up?Someone sure has a lot of time on their hands huh?
I answered after two rings with "hello" - no response and the caller hung up after less than two seconds (probably less than one second, but we'll go with two for the sake of accuracy).
I called back and received the same note about "special phone" or whatever...
I've gotten this call periodically and they just hung up. I think it may be a robocall to determine whether they've reached a live line so they can call later with the expectation of making a pitch.
I got the call again today and, of course, the same result. As I am on OOMA, I promptly added this number to my BLACKLIST, so I won't be receiving any further calls from the number. I also flagged it as a ROBOCALL, so there's a good chance that the number will be blocked nationally on all OOMA telephone systems.