Misleading advertising / bad attitude

Colgate promo specified 'Buy Any 3 Colgate products and received cheapest free' with a picture of various Collate products. Promo did NOT state that only those products were to be bought. Took 3 other Collate items of the same price to till point. Cashier rang it up and no discount was given. Called man named Rodney who then said that the promo doesn't work that way and that I have to take two more expensive items and one cheaper one. Then he collected the promo picture and changed his story stating that what he had just said isn't correct but that it only applies to the products ad pictured. I explained to him that the promo states ANY three Colgate products. Eventually Rodney agreed to allow the cashier to discount me on the 3rd item. He was extremely bombastic about it and the cashier took the promo picture, threw it under a cover at her till point and mumbled something under her breath. I'm terribly disappointed and upset as I had to endure an amount of negative vibes and public humiliation from staff who knew they were in the wrong.