I was wondering how could I achieve a call chat between me and some other person which the other person does not hear me talk but rather the audio file.
Let's say I own an audio file which contains a voice that says "Hello", he will hear that instead of my voice.
Thank you in advanced.
Short answer: NO, this is not possible,
this is clearly explained in the android developer web:
Note: You can play back the audio data only to the standard output device. Currently, that is the mobile device speaker or a Bluetooth headset. You cannot play sound files in the conversation audio during a call.
the reason why, is not explained in the android web but it must be for sure to avoid criminal actions.