1st I convert phone call voice to a .mp3 file here <upload my file>
Then download the converted .mp3 to my phone.
Then mail .mp3 to my gmail account. Then download .mp3 from gmail to my linux computer. Then I can open and play the .mp3 in my preferred Linux media player <eg: xmms, audacious,vlc,smaplayer, etc....>
Read the format on the recorded voice file on your phone after the period/dot to make sure your recorded voice file is supported. But no big deal if you don't. Because if it is not supported. The site will probably inform you it cannot convert the file to .mp3