You can select the following formats when downloading or exporting your file:
WAV (44.1kHz 16-bit)
AIFF (44.1kHz 16-bit)
WAV µlaw (8kHz 8-bit)
WAV PCM (8kHz 16bit)
MP3 (320kps)
MP3 (128kbps)
VOX
WAV ADPCM (8kHz 8-bit)
Please check with your phone provider for which format works best.