To uninstall asterisk-voicemail just follow these instructions.
/debian/stretch/main///install/index.html simple voicemail support for the Asterisk PBX Debian 9.0 comm 1:13.14.1~dfsg-2
sudo apt-get remove asterisk-voicemail
Which will remove just the asterisk-voicemail package itself.
sudo apt-get remove --auto-remove asterisk-voicemail
This will remove the asterisk-voicemail package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for asterisk-voicemail then this will work.
sudo apt-get purge asterisk-voicemail
Or similarly, like this asterisk-voicemail
sudo apt-get purge --auto-remove asterisk-voicemail
|Maintainer||Debian VoIP Team
|Description||simple voicemail support for the Asterisk PBX|