Amr file on telephony uplink

Hi!
I'm new in using Symbian so I apologize if I'll be noob!

Now, I'm writing an application for my Nokia 6630 in order to implement a dialer which reverses an amr file on telephony uplink.

I've read all topic on this forum related to audio problem, but now I've a question for you.

I wrote my code using CMdaAudioRecorderUtility class and PlayL and RecordL methods and compiler compiles it with no problems, but when I try the application on Epoc simulator and mobile phone, they answer me that the function isn't supported.

I've try CMdaAudioPlayerUtility class Play method, and there are no problems.

Only the two methods PlayL and RecordL make meto obtain that answer.
I put my code:

const TUid KMMFExControllerUID={0x101f5022};
const TUid KMMFExDesFormatUID={0x101FAF66};
_LIT(KRecordFileName,"C:\\out.wav"😉;

CMdaAudioRecorderUtility* iRecorder = CMdaAudioRecorderUtility::NewL(*this,NULL,EMdaPriorityNormal,EMdaPriorityPreferenceTimeAndQuality);

iRecorder->OpenFileL(KRecordFileName,KMMFExControllerUID,KMMFExControllerUID,KMMFExDesFormatUID,KMMFFourCCCodeAMR);
iRecorder->SetAudioDeviceMode(CMdaAudioRecorderUtility::ELocal);//ETelephonyNonMixed);
iRecorder->SetVolume(iRecorder->MaxVolume());
iRecorder->SetPosition(TTimeIntervalMicroSeconds(0));
iRecorder->PlayL();

Thanks!