*72 to turn on (you will hear dial tone)
*73 to turn off (you will hear confirmation beeps and get a dial tone)
What I do is press *72, dial my cell number and answer it when it rings. I will wait about five seconds and hang up both receivers. When I return home, I press *73 and the call forwarding is turned off.
I wish I could get this to happen. You would think it is a simple thing, but I have been dealing with problems since Friday. They turned it on for me (five days earlier than I wanted) and now I have been unable to turn it off. *73 just gets "Your call can not be completed as dialed."