False Advertising - Items do not qualify for discount on wednesdays, and they do not indicate it as such on the shelves!!

I go to Builders as a pensioner on Wednesdays to get a 10% discount on my purchases, same as what I do at Game. Unfortunately Builders always has an issue when the items are a little pricey, therefore not allowing the discount on said items, because it is "Below Cost" when one get to the till. There is no way to verify this, because Cost prices are not disclosed. The Add is very largely display that persons older than 60 gets a 10% discount on their purchases. At Game I get a discount even on promotional items, and they both are Massmart "Family It sucks top be lured to buy at inflated prices at Builders, with the hope of a discount, jut to get at the till and told the items do not qualify. Perhaps THOSE items should be identified in advance on the shelves, because it amounts to false advertising!!