If you're
a. NOT living in USA,
b. your carrier supports this feature,
c. in 3G coverage and the other end also,
there is a button in dial pad let you make/receive a video call.
According to your post, you're with Sprint, correct? You don't get it. Video calls are not supported by US carriers like Sprint, Verizon, etc. Unless you are using a phone designed for Europe/Asia and are located there, you can't do video calling. Further, the Sprint version of the Touch Diamond or Pro does NOT have a front-facing VGA camera, so the hardware is NOT there for a phone you'd be able to use on Sprint.