Iphone 5s doesn't ring when called
It's happened several times now, and it's screwing things up for me.
Basically, someone will call my phone, but my phone doesn't ring at all. No vibration, no call incoming notification, nada. Sometimes there's nothing at all, most of the time I just get a missed call notification. And by that I mean I can sit and stare at my phone, and it will just light up with a missed call - nothing else.
It's not set on Silent or Do Not Disturb, it's just not ringing at all.
Please help.
iPhone 5s, iOS 9.2.1