Hello, had same problem with my Samsung S4 Mini,
Problem was so simple I almost felt stupid. But was my second day I had my phone so is a little bit of an excuse maybe haha.
So the answer is go to your green phone button.like you want to call yourself for instance to don't want to disturb anybody right?.Now press call and phone will give message that you can not phone of cause.,No problem. Another menu, your call menu, will appear. Press the button mute mice again. And everything will work just fine,
Good luck. Greetings Herman from the Netherlands,