A new class action lawsuit claims that AT&T “systematically overstated data usage by 7-14 percent and sometimes up to 300 percent” on users’ iPhone and iPad data plans, according to MSNBC. The lawyers for the suit have said that they have spent over US$80,000 testing iPhones on AT&T’s network to prove AT&T’s overstating data usage.

As part of the testing, the lawyers turned off every feature on the iPhone that could use 3G data. Even after shutting off all 3G data connections, there were still 35 transactions for data usage on the lawyers’ AT&T bill. The lawyers say that while the cost to some affected users is relatively small — $10-15 a month — AT&T is illegally reaping huge profits from overstating data usage on millions of iPhone user’s bills.

AT&T has responded to the claims, calling them “without merit.” The company says that the lawsuit doesn’t take into account “automatic app updates in the background that customers may not be aware of.” However, unless they are talking about push notifications, apps don’t automatically update.

Plus, if 3G is turned off as it was in the lawyers’ tests, there is no reason any “automatic app updates” should incur data usage fees.