3 for 2 offer - Mix & Match

I had went to Clicks today and purchased 6 items and was only discounted for 1, the manager said that the cream was not the same. the point of this offer was that you can choose any 3 products of the same range and pay for 2 which did not apply to me when I purchased 5 day cream and 1 night cream of the Johnson's face care products. Its disappointing of the way the manager of the store resolved this. he said it was an error of the ad which I do not believe.