Can't make calls

Second time this has happened. Last time I had to reset my phone to fix it. When I make phone calls, it nothing happens on my end. The receiver gets the call but can't hear anything on my end. I try pressing end call, and it freezes on end call. I can close the app and reopen it, but it's still stuck on end call. I turn my phone off and on, and the same thing happens. Can't make phone calls at all. When people try to call me, it rings on their end but nothing happens on mine. Basically, my 4s has turned into an iPod touch for the second time. I don't want to keep having to reset my phone. Can I get this replaced for free at apple, or what should I do?