I have an iPhone 4S running iOS 5 and cannot find (after trying) any app that blocks calls. Is there anything out there that can block calls on the iPhone?
I have not found a 3rd party application that does this well. You can obviously block a number via your cell carrier. Since I could not find a good method to block calls with an application I ended up adding the number to be blocked to my contact list and assigned a "silent" ring tone to the contact. Although it will not block a incoming call it will cause the phone to play a silent ringtone when the number in question calls. Not a true block caller solution but at least a potential workaround.