Can you actually turn OFF an iPhone? What I mean is, all my old-school dumb phones, you can just turn them off. There was no sleep mode, etc. You turned them on when you wanted to use them, and if you wanted it off, you turned it off. I see there is a sleep/wake button on the iPhone. Is that the same as an on/off button. For example, when it's in sleep, and a call comes in, does it wake up and ring? I'd expect it would. So is there a way to shut the iPhone off?