Hi, the image you are running has many bugs for the voice part, really too much to list here (cfr release notes).
If you upgrade to 12.4(11)XJ4, or 12.4(11)XW5, chances are the issue will be resolved.
Note these releases are not less stable by any mean that generic T release, actually the opposite, being platform specific, bug fixes are incorporated much sooner. Again the proof is in the release notes.
Understand what you are saying, but please note that all of 12.4(x)Tx, 12.4(11)XJx and 12.4(11)XWx, do have a status of "ED" meaning "Early Deployment". In that sense, these have the same "risk status", but 12.4(15)T1 has added features not having anything to do with voice, and is the first maintenante release (the 1 after T).
While 12.4(11)XJ4 means is the fourth maintenance release (the 4 after XJ), hence more has more bugs fixed and is reccomended not only by self, but by the cisco TAC as well.
There is nothing unofficial in both T and XJ/XW or whatever, again the "risk status" according to cisco, is reflected in the LD status.
Then, if you look at 12.4(x) mainline (no T or other letters), the status is LD meaning "Limited Deployment". That is also is different and lesser than "GD" or "General Deployment", a status that no 12.4 version has reached yet.
Of course the problem with LD or GD is that often these don't support the software or hardware features that you need.
Hope this can help in the issue of the releasing system.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...