Did Apple intentionally break an important piece of software on the iPhone, forcing users who wanted to keep using it to either upgrade their operating systems or purchase new phones? A new class action lawsuit alleges that it did, but the reason for the forced upgrade wasn’t to sell more phones. It actually has to do with patent law.

Apple isn’t going to complain if it does sell more devices, of course, but in this case that’s more of a happy (to Apple) side effect. As AppleInsider reports, the real reason for the alleged change was a patent infringement lawsuit that meant Apple had to pay millions of dollars just to let customers keep on making calls using the video chat app FaceTime.

In a previous lawsuit, Apple ended up on the hook for violating a patent held by a company called VirnetX. A 2012 decision in that case led to Apple changing FaceTime so that instead of using the peer-to-peer connection method found to be infringing, it instead routed customers’ calls through a third-party server.

Before the 2012 change, routing FaceTime traffic through that server had been a backup method; only about 5% – 10% of FaceTime traffic traveled that way. Changing it so that all FaceTime traffic went through the third-party servers meant that Apple ran up some huge data bills. Relay fees from its internet provider for this service, Akamai, ran to $50 million in just six months in 2013.

Apple couldn’t really fix that problem, but it could force users to upgrade their phone operating system. iOS 7, which debuted in 2014, used a different data structure for FaceTime that returned the program to peer-to-peer connections. The problem? Some older devices, like any iPhone 4 still in use in 2014, couldn’t handle the upgrade.

The lawsuit cites internal email, including a particularly damning thread between Apple engineers where one explains to another why the Akamai bill would be lower the following year.

“It was a big user of relay bandwidth,” the engineer wrote. “We broke iOS 6, and the only way to get FaceTime working again is to upgrade to iOS 7.”

According to the lawsuit, in public, Apple blamed the problem on a “bug” instead of a deliberate change to the operating system, thus misleading customers. The class-action lawsuit claims Apple violated unfair competition law in California and that it committed “trespass to chattels,” a legal wrong of intentionally interfering with stuff someone else owns.

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