AT&T Withheld information at the time of my order

Okay, so I switched to AT&T. the price was great!  about two months later, i thought, this is such a good price, I am going to upgrade a little so i can watch a show on Cinemax that sounds interesting. I got on line and upgraded. it increased my bill by a whopping $80.00. I lost all my promotional discounts!  I called and asked help to decrease my bill....so now I am paying about $20.00 a month more than I was originally (and of course no cinemax...the show wasnt that good anyway). 

Why didnt they tell me that if I made any changes to my account at all that I would lose all my promos?  Seems like this would have been easy to communicate to me!  GRRRRRRR!