I received a call about 5:20 pm and answered it, since I was expecting a call on that line, but was away from caller id. I spoke two times, could hear voices in the back ground, the other party said nothing and then hung up.  I got a call on another line and saw the same number appear on its caller id.  Seems to confirm conclusion of previous person who commented. My other mailbox is full so dont know if they tried to leave a message. I called the number back two times after receiving the second  call from them and got a busy signal both times.