Unfortunately for AT&T unlimited users, the last few years have seen their data throttled after 5GB no matter what, even though AT&T's own policy stated that throttling would only occur in times of network congestion.
The new policy allows up to 22GB of data per month, uninterrupted, afterwards which AT&T can throttle if there is network congestion. This follows in the new net neutrality rules that allow for "reasonable network management" although AT&T is likely only making the move because the FCC has proposed a $100 million fine for the carrier's abusive throttling for unlimited data subscribers.
Source:
AT&T