Robo Stop

Using a small program like "Asterisk" or something similar, you can have any incoming 800, 877, 866, etc calls get screened. Using voice detection software, you can have a pre-recorded "hello" played when the system answers. If no response is given within 2-3 seconds, the call gets hung up on. If someone responds, a second message is played that says something like "Please hold while we connect you". Repeated calls from the same number can be added to a block list that the system automatically blocks once its seen it 3+ times.