Receiving a spam call puts you in a bit of a dilemma, or at least it does for me: How do I deal with this call that doesn't alert the spammers that this is an active number that they can call again? Answering the call is obviously the wrong choice, but I always assume that rejecting the call outright will also be detected as a deliberate action and therefore a person is on the other side. Some people have suggested answering the phone but not talking, so they think it's a dead number, but I want something more definitive.

My idea is to have a "spam" button on the incoming call screen, that answers the call but doesn't connect the microphone. Instead it plays either the standard "the number you're dialing is not assigned, please check your number and try your call again" recording, or a fax/modem sound to make them think the phone number belongs to a machine and not a human.

Would this work? Or would they still be able to determine that the recording is spoofed by the phone itself? Does anything like this already exist?