iPhone 4S
A customer showed off her new iPhone 4S as she left an Apple Store in New York last year. Reuters

AT&T has already begun throttling unlimited plan owners who use more than two gigabytes of data per month, but only if those people are in an area where data usage is heaviest on the AT&T network, The Associated Press reported Monday.

Anyone with an unlimited plan among the top five percent of heaviest users in their areas are having their download speeds choked down to about one percent of their former speeds because of increased traffic on AT&T networks, company spokesman Mark Siegel told the AP.

That means anyone using more than two gigabytes of data per month is subject to the super-slow speeds.

AT&T stopped selling the unlimited plans in 2010, but unlimited plan users were warned in 2011 the company would be dialing back download speeds of the heaviest users. Sometimes that means a slower network in the middle of the month, even if you haven't gone over the two gigabyte threshold yet, the report said. In other words, once you cross the line, AT&T will choke down your data speeds for the rest of the month, making using a phone for more than voice or text nearly impossible.

This all comes on the heels of AT&T's failed takeover of T-Mobile, and the recent revelation all three of the largest U.S. mobile broadband providers were losing billions of dollars on the iPhone.

On Sunday, AT&T doubled its activation charge on phone upgrades, from $18 to $36.

Unlimited usage on Verizon is handled much differently, and a busy network there will result in slower speeds for those top five percenters, but it is not brought to a near standstill. Sprint, on the other hand, still offers an unlimited plan to new users, but the speeds on their smaller network are slower on average than AT&T's network, and they lack any 4G LTE capacity.

Tell us in the comments if you use more than 2GB of data on AT&T and if they've notified you or throttled your service.

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