There are 2 ways to do this: go to the Call Transfer Information screen. EXTERNAL
Sequence to initiate transfer !,#3,,
Sequence to complete transfer !,#3,,
Sequence to transfer 3 way call !,#3,,
OR
EXTERNAL
Sequence to initiate transfer !,9,
Sequence to complete transfer !,3,
Sequence to transfer 3 way call !,3,
MAKE SURE THAT YOU ENABLE ANY EXTERNAL CALL FWD, TRANSFER OFF PREMISE OR CONFERENCE CALLING THAT YOUR PHONE SYSTEM HAS.
Hope this helps