Bad service

I was at checkers hyper N1 city mall today, I wanted to buy a small Nescafe coffee that was R40, when I got to the till the coffee did not scan, I waited for almost 30 minutes only to be told that the coffee was not for sale, after they waisted my time and I was on lunch break, not even an apology was given, my question was why did they put the coffee on till if they were not selling it. I am still sitting here without coffee because it was the only small coffee that I could afford.