Cetaphil products/clicks Brooklyn

Went to clicks Brooklyn to buy my cetaphil products, got special of 3 for 2. Happy was me until I went to the till only to be told that the 1n box that has 2 products inside does not apply for the special. I took the box and 2 foam washers and now I had to return the box, I asked them nicely why is not written in that tag thing of their, the respond that I got was it is not their duty to fix that. I was soo shocked by the response then I said please whoever responsible for fixing the matter to fix it and they sad I have to write an email to clicks I know for sure that was an unfair treatment I don't mind not getting a burgain but cold responses like that they make me think twice abt buying at any clicks store. I have a picture of the tag and my slip for purchased products. Don't know where to attach them here.