When you receive unwanted calls, just say, "Just a Minute", then lay the phone down and come back to it after a few minutes and they will have hung up. Hopefully they will take you off their list. I have just tried this and hope if I continue to do this that I will receive less and less unwanted calls.
These people (if there are even real people on the other end of the line) call at all hours of the day and night and hang up just when the answering machine kicks in, creating an annoying tone that then ends up on my voice mail .ARGH. Am sure these are robo calls (the "machine"/software doesn't care what time it is) but you'd think that after dialing the same number over many days and weeks and always getting the answering machine, someone would write a program that would delete the number so the calls will stop. This surely can't be doing the caller any good to have so much bad publicity. Annoying now doesn't begin to describe this group.