Apple is already facing one class action lawsuit alleging that customers were unknowingly using up substantial amounts of mobile data, and it now faces a second.

The issue at stake in this new suit is that the iPhone 5/5s could silently switch from Wi-Fi to LTE under some circumstances, resulting in mobile data usage even when the phone was on Wi-Fi. This was fixed for Verizon users back in September 2012, but law firm Hagens Berman Sobol Shapiro LLP claims that Apple didn’t fix it for AT&T users until more than two years later.

According to the complaint, filed in the U.S. District Court for the Northern District of California in San Jose, Apple knew about the defect “almost immediately,” yet failed to fix it for AT&T wireless subscribers for years, and did not even disclose the defect. The defect affected all versions of iOS 6 and 7 and was only resolved with the release of iOS 8.1 in October 2014.

The firm said that the problem occurred when streaming video, when the phone was working so intensively it shut down other functions to cope, causing it to switch off Wi-Fi. (Swift here refers to the name of the CPU on the A6/A7 chip rather than the programming language.)

In the iPhone 5 and 5S, when a consumer streamed high volumes of data for a period even as short as a couple of minutes, the graphics processing unit (GPU) would take over all video decompression, decoding and presentation to the display. Because the Swift central processing unit (CPU) no longer played a role in the video decompression, decoding and presentation process, the Swift CPU would go to sleep to conserve battery life. Once the Swift CPU was asleep, the iPhone 5 and 5S would automatically switch from streaming data via a Wi-Fi signal to streaming data via a cellular signal.

Hagens Berman Sobol Shapiro LLP said that because Apple was allegedly aware of the defect but failed to either fix it or warn customers, the company violated California consumer laws, “including the Unfair Competition Law, the Consumers Legal Remedies Act and the False Advertising Law.”

Anyone wanting to join the class action suit can do so via the firm’s website.

Photo: AnandTech