ear bud problem

I have an iPhone 4S and prefer to use the ear buds to make and receive calls as well as communicate with the phone. Howver, for the past several weeks, the ear buds have not worked. I got another set, and this also did not work so I got an Apple set the other day. Still the microphone does not pick up anything I say to the phone such as a call or question. Sometimes even without the ear buds and just pressing the home key the phone does not seem to hear what I'm saying. Is there a setting that has gotten messed up or is there anything I can do to correct this problem? It worked well for at least a couple of years.