AT&T’s questionable policy with regard to unlimited smartphone data plan holders recently found its way back into the limelight following a new wave of subscriber complaints. The nation’s No.2 carrier no longer offers an unlimited data plan to smartphone users, though many subscribers on its network still have grandfathered plans that provide an unlimited amount of smartphone data each month. Subscribers who approach the top 5% of unlimited data users in a single billing period see their data speeds throttled, however, and countless users have found that AT&T is now beginning to throttle users after less than 2GB of data usage in a billing period. According to a new study, subscribers are right to be furious at AT&T because throttling does nothing to alleviate network bandwidth issues. Read on for more.

Wireless bill analysis firm Validas extracted data from more than 55,000 cell phone bills belonging to AT&T and Verizon Wireless subscribers from 2011, and the firm sought to determine whether or not data throttling is necessary. According to Validas’s findings, throttling may indeed simply be a ploy to push unlimited users into newer tiered plans.

“When we look at the top 5% of data users, there is virtually no difference in data consumption between those on unlimited and those on tiered plans—and yet the unlimited consumers are the ones at risk of getting their service turned off,” Validas wrote in its report. “So it’s curious that anyone would think the throttling here represents a serious effort at alleviating network bandwidth issues. After all, Sprint does seemingly fine maintaining non-throttled unlimited data for its customers.”

Verizon Wireless subscribers on unlimited smartphone data plans actually used less data on average than those with tiered plans according to Validas’s data. The opposite was the case at AT&T, however the difference was 0.78GB on average and median data usage varied by 0.53GB.

AT&T is not the only wireless carrier in the U.S. that throttles smartphone data speeds for unlimited data plan holders, of course. Verizon throttles the top 5% of unlimited data users and T-Mobile throttles its smartphone subscribers after 5GB of data usage in a single billing period. AT&T has drawn the most attention of late because it has been throttling unlimited data plan holders after less than 2GB of usage in many cases. AT&T offers a 3GB tiered plan for the same $30 per month that unlimited plan holders pay for 2GB of full-speed data or less, however the tiered plan offers 3GB of full-speed data.