BB Bold :: No Voice Function 9900?

I am a T-mobile subscriber having serious problems with my 9900's voice function for both telephone calls as well as dictating emails and texts with VlingoPlus.The specific problem is that anyone I call or who calls me cannot hear me or they hear a garbled indistinct voice.I have experienced the same problem with two replacement 9900's which T-Mobile sent me (one in July 2012 and the second in September 2012)This problem first arose with the first replacement 9900 I received in July 2012 which replaced a 9900 which was experiencing intermittent ongoing failures of the blackberry internet service connection.The first replacement 9900 then began to have problems with the voice function shortly after I set it up.Although T-mobile's technical people attempted to assist me they failed in their efforts and they simply sent me a second replacement 9900 several days ago.I set up the second replacement 9900 on September 16, 2012 and the voice function failed the same day and has not worked since.I have done battery pulls but the problem persists.Today per T-Mobile's recommendation, I obtained a new SIMM card.There still is no voice function?