Why can't I hear the ring when I'm calling someone?

I have had my phone for a few months now its pretty new and it's an iPhone 4S but when I call someone I can't hear the ring? It has never done this before it only started today. Why is it like this is it broke or something I can hear the person talk just not the ring when you call someone? Why is it like this? Is it broke? How can I fix it? Does it turn on and off and if it does how do I turn it on?
Oh and when I put head phones in it does the same thing.

Your phone speaker is probaby broken

CAn you see what rong with my iophone 5c is not rings or i csnt not make cslls

I'm having the same problem. When I call out I can't hear the phone ringing. Then they answer