Yes, it is on data plan with ATT. I've been a BB user for several years now. I have always had no trouble enabling and using the function of call waiting. However, when I unlocked the Storm the function is no longer available. These are the steps I have tried:
The following options are available:
General Options, Voice Mail, Call Logging, Smart Dialing, Speed Dial Numbers, TTY, Enhanced Audio, Sounds
However, the Call Waiting and Call Forwarding functions are not listed as an option.