When you add an extension that already exists the voicemail.conf file gets overwritten BEFORE it notices that that extension is already in use. This doesn’t seem quite correct. Happens on FreePBX 2.3.1.
Please report this in the bug tracking system. It is the one place where it is tracked and followed.
You can find it on the left hand side under development site, report a bug.
Please provide as much detail as possible.
it’s addressed in 2.4 and I’m probably not going to fix it in 2.3 because the solution in 2.4 depends on the new extension registry. (2.4 is svn trunk, which I hope to go official beta within a week or less.)
Philippe Lindheimer - FreePBX Project Lead
http//freepbx.org - IRC #freepbx