asterisk users - Dec 2003 - Voicemail messages and codecs

If I call to voicemail with G.711, I'm getting the unavailable message
I've recorded in voicemail.
If I call to voicemail with GSM, I'm not getting my message, only
thevoice's standard message
that always says user zero-zero-zero-zero regardless of extension.

Do the user need to record a message for every possible codec or do I have to
read the manual?

How do I change zero-zero-zero-zero to the user's extension?

/O