Investigate AT&T wireless practice of limiting data usage on so called "unlimited" plans.

I'm an unlimited data plan subscriber with AT&T that abides by their policies. Recently got a text message stating my data usage on LTE unlimited plan will be throttled if it exceeds 5GB. After is exceeded 5GB, they made all of my application virtually useless by how slow it gotten. I signed a contract under the impression that the data is unlimited and want AT&T to honor their part of the agreement. The reason why I use that much data is due to my job and amount of emails I get, various streaming services from iTunes Radio, Spotify, Netflix, Hulu, Redbox Instant, Amazon Prime, Amazon Cloud, Google Music and so on. The world is moving to the cloud and so AT&T needs to accommodate these services unlimiting my data usage. I've been a customer for over 7 years and have had unlimited plan.