I tried RoboKiller but it didn't work and I still received robo calls, 3 on the first day. It blocked 0 robo calls during my 6 days of trial. It is ineffective because it uses white lists and black lists and the robo callers use spoofed fake caller ids. I'm unable to block all 10 million phone numbers in the same area code, and I may want to speak to the real owners of those phone numbers some time in the future. (In fact, I rejected a real caller from my same area code thinking it was a spammer.) I would like an app that is able to block these calls, perhaps by obtaining the real caller id the same way police are able to trace calls. Ideally, I would like a service that presents an audio CAPTCHA. I have that feature on my land VOIP ("Press x to complete your call") and I receive absolutely 0 spam calls.