Is there an app for that?

Ok, I just got an Iphone 4 (with AT&T if that makes any difference) and I am looking for an app that I can place specific phone numbers on a block or automatic reject list. I don't want an app with fake voices telling them they have the wrong number or one that has predetermined telemarketer numbers. I want one where I can choose the number to block, and one that will send them directly to voice-mail or better yet disconnect it all together. 10 pts goes to the 1st legitimate app. Thank you!!