If I call you at 3 am every morning, it wouldn't be harassment then? Considering you have allowed those calls by signing up for a service.
If you call me tonight at 3AM it would be very rude. Calling me every night at 3 would be harassment. I could easily have the phone company identify you (no matter you did at your end) and have them tell you to stop. If a telemarketer did what you suggested I would ask them to stop and they would. The problem to people here seems to be that there are so many telemarketers they want a way to tell them all to stop preemptively.
Well, I figured out one way: buy cell phone service, and give up the land line. There would be many other ways if telephone service was deregulated, but instead we are talking about adding more regulation. It's actually pretty pathetic.