Hey "The Mom", I remember the old soda fountains and ice cream parlors.
(You sure you are old enough to remember those days? Or hearing stories from much older siblings!)
So I call it soda also. My cousin who grew up in Canada calls it "pop'.
Some other relatives call it soda-pop so the discussion goes on....
I used to stop by the soda fountain in the drugstore in "The Square" in Riverside, RI frequently. Five cents for a soda, back in the 50s & 60s.
And back in those days, a milkshake in RI was just milk, flavoring, and soda water whipped up. If you wanted ice cream in it, you ordered a cabinet.