There are many things in India, which is just a marketting gimmick. They measure battery by Talktime. By 3G talktime, they means Talktime on 3G Network. Not Video Calling, but just Voice Calling.
Regarding Video Call, many peoples do not have idea about difference between Video Call over 3G Network and Internet.
You can only get, Video Calling over 3G network on few models of samsung. They managed to do something on the firmware level, and it's solely their RnD and build by them. And it exists on few models (Galaxy R which I can think of now).
BTW looks like Galaxy Advance supports Video Call : Samsung Galaxy S Advance - Make a video call
It'd be better if you can check before buying. Consider buying from store. Or you can go to a store check it out and buy online if you want to.