Didn't we just hash this out a few weeks ago?
Anyhow, generally (there are exceptions though) people from the East and Midwest call it "pop." People from the West and Southwest call it "Soda." And people from the South call all carbonated soft drinks "coke."
I've called it all three, since I've lived in the West, South, and Midwest. Funny how local customs grow on you after a while, isn't it?