No Caller ID

Phone rang 6:30 am this morning, I didn't pick up, the answering message played, but the caller left no message. A hang up caller or a caller leaving a crank message is not unusual or even a crank caller blocking his/her phone number ID is not unusual, but what is somewhat unusual is not getting any message on the screen that the caller's phone number is blocked or out of the area covered by caller ID. Instead, the answering machine picked up, played the message, and then recorded the silence all without displaying anything on the caller ID screen other than the day, date, and time information.

Other than the usual, such as people complaining about an incredible echo on my phone or else asking if I'm on speaker phone when I'm not, the unusual has began occurring again. For example, the phone will start making the noise as though knocked off the hook and when I go to hang it up I notice that it's still on the hook. Once when trying to stop the noise, I picked up the receiver and distinctly heard someone on the other end of the line hang up. IMO- that's unusual. I wonder what "they" are trying to do?