Looks like I'm not the only one with this issue.
We upgraded around January 2014 (I believe) to the iPhone 5. One of the conditions to my pulling the trigger on the upgrade was that we keep our unlimited data plan (I was assured by the sales rep that we would).
In August I started getting messages that I was approaching my data limit (I thought it was just a sales thing, so ignored them), then I got charged. Long story short, I chatted with an AT&T rep (in August) and was told that he would send a case to a "specialist". A couple days later I received an email saying that there was nothing that they could do since the "feature has been off the line for more than 90 days". This really feels like the standard bate and switch sales technique (i.e. The sales person tells the customer one thing, then once the sale is done, the company makes a change behind the customers back and by the time the customer notices, it's "too late" to fix it). I had hoped that a company as established as AT&T would be above this kind of thing, I’m hoping that when I contact them again they will confirm my hopes.
I’ve been with AT&T for a lot of years and don’t really want to switch, but it feels wrong that I should have to spend my time trying to convince AT&T to honor there agreements.