Over the weekend we needed to Call Forward one AT&T Cell phone to an other...
The mobile handset we were doing call forwarding on, was Windows Mobile Enabled BlackJack phone, and it was on the OLD AT&T network (Former AT&T Wireless Customers/Old Blue AT&T) so the the following link had the answer...
http://www.wireless.att.com/learn/basics/choosing-features-services/call-forwarding.jsp
If that does not work for you, checkout this link.
http://www.att.com/gen/general?pid=3733
