treating customers unfairly , selling expired goods

I bought Sunlight laundry soap from Usave in Ga-Rankuwa - when I got home , I was drawn to the packaging that when you buy 4 bars you get R10 Eskom electicity voucher but surprisingly the competition ran from 15/09/2016 - 31/12/2016 - I called the unilever number ********** 062 where they told me that the soap has expired because they asked for some numbers which I gave them- Usave had over 20 boxes of those soaps which they are selling @ R10 and most of the people staying in the area are aged people who are not aware.