Did the bartender cheat me?

The sign outside the place probably said wells or house drink like if you go to Chili’s I can order vodka and sprite & get it for like $3 dollars but whenever you ask for a specific liquor usually you wont ask for something cheep they will give you premium liquor like Grey Goose and now you will pay $6 to $8 dollars per drink now it sounds like the bartender added the alcohol to your previous drink which is very unprofessional if he did. Also the cup was probably a small one you were really paying for the alcohol not the soda. Hope this helps.