If you get a recorded message when you answer the phone, that is a Robocall. The best thing to do with them is just hang up and report them to ftc.gov. Telemarketing calls are a little different. I had heard that being on the do not call list expired after a certain amount of time and you had to do it again, but not sure about that. If you answer and there is a pause before someone comes on the line, that means that they are on a dialer system - their dialer just keeps dialing numbers until it detects someone answering the phone. If you don't answer, a message is not left, the dialer just keeps doing its job and moving onto other numbers. It's irritating that the phone rings though. I just want to be left alone!