オリジナル投稿者： khuong hoang ,
I have figured it out! Its caused by a bad simcard connection. Do this, open the back of the phone. Make call to another phone and put that speaker on. While calling , press down on the back of the circuit board where the sim card lay, right where the clear plastic tab (to remove the battery is) and press down on that. You'll notice that the mic then will work. So put the cardboard precisely there, adjust thickness to get it to work. Good luck!