The ringer volume settings can be changed using the volume keys on the outside of the phone, even when the phone is closed. I find that when I carry the phone in my pocket, the buttons get pushed randomly by bumping up against other things in my pocket, and the phone gets switched to silent mode once or twice per day. This often leads to missed calls if I don't remember to check the setting regularly. Does anyone know how to disable the volume keys? There is no obvious reason that one should not be able to inactivate these keys when the phone is closed, but I can't figure out how to do it.