False Advertising

On 06-10-2015 I purchased beef schnitzel which had a 30% discount sticker on it as well as the 10% rewards discount, without checking my receipt I assumed the discount was given. Upon returning home I checked the receipt to find I only received my 10% rewards discount. My concern is just that how many other customers aren't being fooled by thinking they are getting discount and they not simply because most people don't check their receipts!. In future rather just have the usual rewards discount only.