Ability to edit sip.cfg file for Polycom phones within EPM

Need to have the ability to edit the sip.cfg file within End Point Manager. I wanted to figure out how to turn off the message waiting beep and this is within the sip.cfg file.

This is possible. Just edit the file in EPM.

Which is totally possible. The problem I am having is that I go into EPM, base file edit. In this I am not seeing sip.cfg first of all. When I try to ad a custom option using the add setting I put in sip.cfg as the filename. Nothing gets written to the sip.cfg file nor any other file.