False Advertising Competition

I went to Engen Emmarantia on Saturday 13 February 2016 to purchase something to eat. I needed goods for about R30.00 there was a poster at the chiller indicating if I spend more than R100.00 I can win a Valentine's Teddy Dog. So I grabbed a few more items and paid R120.00 instead, thus I reading the sale. After the purchase when I queried the competition, I was told sorry it is over. There was no date on the poster. I therefore spent R90.00 more under false advertising. I couldn't get a refund as it was at night and there is no supervisor. This is completely false and against the CPA luring me to spend money with false advertising.