I will get a voice mail on my S5 and my phone didn't ring and doesn't show a missed call. I'm in sales and every call is important to me. Yesterday I was sitting in my office and my phone beeped and I had a voice mail from an important client telling me to call him back and I didn't have a missed call and it never rang. Another example is 2 weeks ago I was traveling and my wife tried calling me 3 times, my phone never rang nor did it show a missed call. She called the person traveling with me and that's the only way I knew she was trying to call me.I seem to get 1 voice mail a day without receiving a call or showing a missed call.
