There's an AT & T cell user that can call me, but when I try to call him back, I get a robo-voicemail response telling me I've called the number and to leave a message. The recipient never hears the message or sees that I have called.
Make sure that he doesn't have Do Not Disturb enabled if he has an iPhone. Make sure that he doesn't have you blocked or that he doesn't have call forwarding on.
