As promised, AT&T has started throttling unlimited plan customers who consume an excessive amount of cellular data.

Back in June, we heard that AT&T was aiming its crosshair at unlimited customers who were in the top five percent of the carrier’s “heaviest data users,” and that the company would begin firing from October 1. As outlined in AT&T’s official statement, which hit the Web in June:

One new measure is a step that may reduce the data throughput speed experienced by a very small minority of smartphone customers who are on unlimited plans – those whose extraordinary level of data usage puts them in the top 5 percent of our heaviest data users in a billing period.  In fact, these customers on average use 12 times more data than the average of all other smartphone data customers.  This step will not apply to our 15 million smartphone customers on a tiered data plan or the vast majority of smartphone customers who still have unlimited data plans.

Starting October 1, smartphone customers with unlimited data plans may experience reduced speeds once their usage in a billing cycle reaches the level that puts them among the top 5 percent of heaviest data users.  These customers can still use unlimited data and their speeds will be restored with the start of the next billing cycle.  Before you are affected, we will provide multiple notices, including a grace period.

Now, it looks like the process of limiting the data usage of so-called “data hogs” has begun. As you can see in the above screenshot, one AT&T user has already been warned by the carrier, and will likely “get throttled” as a result.

This isn’t something limited to just AT&T. In fact, Verizon is also planning on targeting its heaviest data users, too. Let us know if you’ve received a similar message from AT&T in the comments.

[via 9to5Mac]