Called twice, left no message

Called, didn't leave a message  and DIDN'T HANG UP. Line has been "in use" for an hour.

Calls repeatedly for a few days. Then stops. Started again today after a lapse of a month or two.
Never leaves message.

Calls twice a day and leaves no message.  I don't answer nor call back.

dozens of calls from this number. At least a half dozen a week. Brief noise at the beginning, then a silent pause, a male (not sounding very intelligent) saying, "hello..........hello" and then the call ends. Called today at 2:43 (Sunday) and again exactly 2 hours later at 4:43. I was finally there to answer this time. I heard the noise and said,"hello", there was the pause as I repeated "hello" a couple of times. When I heard the same double hello that I heard on my machine, I said "Hello, idiot can you please put me on your no call list!". Surprisingly the guy replied and said yes he would do that. The message is exactly the same in every instance, so it is an automated call, but apparently there is someone there.