Good lap dance poor communication

This is a decent club offering a 15 dollar lap dance plus 5 dollars for the booth area where they give the lap dance. I asked for one lap dance thinking I was going to get one song for fifteen dollars. However being quite drunk I wasn't paying attention to the song that was playing. When offered a back massage I asked how much more that would cost. I Can't remember what it was but I declined and and then was charged 40 dollars by her which mad me upset so I paid and left with my friends who were waiting for me.