people can't hear me & I can't hear them when calling
Telephone fully functional & everything works except when i make AT&T phone call: people can't hear me and i can't hear them.
Facetime, Viber, tango, Music, Youtube.. all sound systems works except phone calls.
I contacted AT&T and changed sim card; problem Not solved
I contacted Apple Support they suggested to restore phone, i did; problem Not solved.
Any ideas ?