How would i go about changing the DN? I know that this phone use to go to an employee here. The extension use to ring in his office. He had to leave for a while and somehow however it was setup before it is no longer setup that way now. Also, now that he is back he wants the same number.

I do know if you call his old number it rings to his old voicemail account. I know if i call it from the outside world it goes directly into his voicemail.
Any help is greatly appreciated.