Hi. After i'd tried this code to convert GSM to MP3, It was converted successfully but when i tried to play, there's no content.
sox -t gsm -r 8000 -c 1 -e signed-integer 003533-dialer-Feb-01-2017-16-00-17-PM.WAV -t wav -e signed-integer 0017.wav

file 0017.wav
0017.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

sample output.
sox 0017.wav -n stat
Samples read:                 0
Length (seconds):      0.000000
Scaled by:         2147483647.0
Maximum amplitude:     0.000000
Minimum amplitude:     0.000000
Midline amplitude:     0.000000
Mean    norm:              -nan
Mean    amplitude:         -nan
RMS     amplitude:         -nan
Maximum delta:         0.000000
Minimum delta:         0.000000
Mean    delta:        -0.000000
RMS     delta:        -0.000000
Rough   frequency:  -2147483648
Probably text, not sound

I cannot play the converted mp3 file.

I don't use SOX so I can't comment much about that. Is the .GSM file up on the web so I can try using other tools?