Manually dial voice mail using 999#. You may need to alter the number of "9"s dialed to correspond to the normal length of extension numbers used by you your system. So, if your extension is 10, then try 99#. If your extension is 1010, or 4 digits long, then try 9999#. The # is typically used as a "send/dial" key command and I am also assuming that your system admin continued to use the default 9 number for voice mail.