Was having same problem with my iPhone 4S. All setting were on the correct way and slider button on side was on (covering red dot), phone would not ring when someone called, wouldn't ring when someone would text, music wouldn't play and volume for videos wouldn't play either. When pressing the volume button on side to make it go up or down, it would show the speaker but no volume control line. After trying everything under the sun. I googled it and guess what a simple fix and sounded kinda crazy but was willing to try anything. Press the right side of the corner of the phone by the home button a few times. Did this and finally started working. Hope this helps someone else out.