Pop, to my knowledge, is a Yankee term. I used to work for a man that called all soft drinks "Pepsi", while everbody else I knew said "Coke". 'Twas confusin'.
I will occasionally hear someone speak of a "sody-water" (usually trying to be funny), but I have never heard anyone say "soda".
But then, Arkansas is a fur piece north o'here. Mebbe they been infected by Yankee-speak.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.