looks like someone here had the same problem: https://community.verizonwireless.com/message/953942 The result was a new phone.

if you found your apple iphone defective, i would try to bring it back to the apple store . From there, you would know the problem and the solution for it

Sounds like something broke internally. I would take it to an Apple store.

I have now done a full reset and still no sound

I was in the middle of a phone call with the speaker on and while talking the sound cut off. I thought the call had dropped but I have since found that it did not. The speaker just stopped. Since then no sounds are working. I have rebooted the phone several times and even reset all settings. I have done some research and found that this is a common problem. I can find no way to get it to work again. Anyone have any suggestions?