While talking the other person cannot hear my voice

A little more trouble shooting is required on this. Have you tried it with a Bluetooth headset to see if your voice transmits? What about on speaker phone? Lastly try a wired headset with a microphone. If your voice can be heard on all three of those methods, then most probably you have dirt or debris in your microphone hole. I'm assuming that the phone has never been worked on. Try using a dry tooth brush to clear the holes at the bottom of the screen of debris.