How can i perform phase coding of an audio file?

I am working on audio steganography using phase coding. I read a wave file as x=wavread('filename.wav') then I perform fast fourier transform on it X=fft(x);

now how i manipulate on the array Xphs=angle(X); now when i ifft() on the new phase (say Xphsnew) i do not get the new phase. Rather i get back my original phases.

Can you please help..please...i need help on how can i hide data usig the phase

pleaaaase help mee...