STYLETHREAD -- LET'S TALK SHOP!

It usually only works if the person is on the same network (i.e. same company) as you. What you have to do is call into your voicemail box and wait for the menu option "to send a message" (if this doesn't come up, hit 0 to hear the full list of VM options) then it will prompt you to enter the person's phone number and to leave your message and then press # or *. I think if it doesn't work you will get a message saying it was unable to deliver, however it might take a little while for that to come through.