Maybe you pressed mute you can do hat when you make a phone call not haveibg the numbers shown there is a keypad that says mute speaker FaceTime and other stuff. When in a call try to have the number keypad on to make sure your not muting it.
It could be a receiver issue like a speaker. I had a problem that I couldn't hear anyone unless I used speaker phone. This is known issue and maybe yours is to. If your within 14 days I would go to the apple store if they confirm something could be wrong exchange it for a new one where you bought it. If not within 14 days you can still go to the apple store and in 10 mins they will tell you what's wrong. If not you can call Verizon and replace it.