I personally call it Cola, rather than Soda, and I've never heard it called Pop, other than from, well, Americans.
I would use Cola in general, or Fizzy Drinks, or Soft Drinks.
Otherwise, I would refer to it by brand. I want a Coca-Cola or a Pepsi, or a 7Up or a Lilt, whatever I want.
But, to answer your question, I would have to choose Soda over Pop, as Pop sounds absolutely stupid.