The app for answering and making phone calls has just disappeared off my son's phone. If someone calls him, the phone rings but there is no way to answer it. He can place a call from the contacts app, but there is no option for dialing a number without a contact attached. Checked for updates, nothing outstanding. (Indeed, it seems like it may have been right after the last update that this became a problem). Anyway, any ideas on how to fix this?