Head & Shoulders Shampoo - Persistent Dandruff Despite Promises

My dandruff problem has been bothering me for years, and despite using Head and Shoulders shampoo, I haven't been able to find a solution. I have followed the directions for use, and despite the fact that the product promises to eliminate dandruff completely, I have not seen any improvement in the condition. Where is the outcome that is absolutely guaranteed? I believe that your advertisements do not accurately reflect the situation and instead mislead your customers.