Swiss privacy software company Proton on Monday sued Apple in U.S. federal court, accusing the technology giant of maintaining an illegal stranglehold on iPhone app distribution and charging excessive commissions to app developers.

Tier 1 of the Store Services fee will provide developers with only basic App Store features for a cheaper, 5 percent commission on in-app purchases, including app reviews, privacy nutrition labels, and access to Apple Support.

Apple is changing its App Store policies in the EU in a last-minute attempt to avoid a series of escalating fines from Brussels. The $3 trillion iPhone maker will allow developers in the bloc to offer apps designed for the iOS operating system in places other than Apple’s App Store, the company said.