You should be able to, you'll just need to both have apps that support it, such as Skype, BBM, Viber, Whatsapp, or Facebook messenger.
I don't believe Samsung has this feature as a native app or feature, BUT I'm not sure.
EDIT: I'm told AT&T has a video calling feature. I have no direct experience with this, but this is what I have been told. I can't imagine why it would not work on both devices provided they both are AT&T.