Rude and un helpful service

I downloaded the kauai app as I heard that if it was downloaded that I could acquire a free smoothie.I approached the counter and told them that I downloaded the app and it had told me on the app that I could go claim my free smoothie, the person told me that I could only choose from 3 categories (app did not specify this) in acceptance I chose a smoothie. The person left to attend other business leaving me in the company of a different employee.This employee then proceeded to take my order and then told me the price for the smoothie, I told him that I downloaded the app and he rudely responded with\you could've told me that!"I proceeded to show him the bar code on my phone to scan from the app . He then told me that I could now only choose from one category made up of 3 choices.We argued about this for a while and he proceeded to tell me that it was my job to inform him about the app.I then chose a smoothie from that category and he told me that the one I had chosen before was already being made.I told him that this was not my problem.A further argument went on and my friend decided to buy the smoothie that was already made.Barcode was scanned and he asked me to pay extra R1. """