I think it depends on what type of phone people think he has. Don't know if iPhone has a "talk to call" function, though I've seen it on other phones. With iPhone, VoiceOver would speak to him which buttons he's touching, and I'm pretty sure there are specific swipe motions for calling once he's chosen which contact he wants. VoiceOver and Speak Screen also work for typing text messages/e-mails or reading back things to him on screen. There's also regular dictation for sending text messages (where you speak to the phone and it writes what you say).