My iPhone5 has no sound when others call and send text messages. What's wrong with others listening to music and watching movies?

There is no sound when making iPhone5 calls, but there is sound when listening to music and playing games. This situation should be that the mute button of iPhone5 was pressed by mistake. The way to return to normal mode is to press the button on the top left of the front of iPhone5, not the red area! If I can help you, please click "Like". Thank you!