(Bloomberg) — Apple Inc. further escalated its fight with Epic Games Inc., filing a countersuit to stop the game maker from using its own payment system for Fortnite.Apple is seeking monetary damages to compensate for its loss of fees, according to a filing Tuesday in federal court in Oakland, California.“Epic fired the first shot in this dispute, and its willful, brazen, and unlawful conduct cannot be left unchecked,” Apple said.Epic last month launched a payment system that circumvented the Apple App Store, so the iPhone maker didn’t get a cut of purchases inside of Fortnite. Apple then stopped new users from downloading Fortnite on its platform, but existing copies of Fortnite can still use Epic’s system.Epic sued Apple on Aug. 13, claiming the removal of the Fortnite app from the App Store is “retaliation” for the game maker’s decision to offer in-app purchases through its own marketplace. Epic was denied a court order that would have temporarily stopped Apple from delisting Fortnite.Epic declined to comment on Apple’s filing, while reiterating its position that it’s trying to compete in a fair marketplace by offering Fortnite players a direct payment option and passing the savings on to them.Read More: Epic Tries New Gambit to Restore Fortnite in Apple App StoreThe case is shaping into a major antitrust battle over tolls of as much as 30% that Apple charges developers when users make in-app purchases. Epic has filed a separate suit with similar claims against Google.”Although Epic portrays itself as a modern corporate Robin Hood, in reality it is a multibillion-dollar enterprise that simply wants to pay nothing for the tremendous value it derives from the App Store,” Apple said in its filing.Apple said Epic’s actions have hurt its business and customer relationships.“Epic’s conduct actually interfered with Apple’s relationships with its consumers, in particular those who made purchases through Epic’s unauthorized external purchase mechanism, by depriving Apple of the economic benefit that it reasonably expected to receive from those relationships,” according to the filing.Contradicting Epic’s claim that the App Store is anti-competitive, Apple said it provides a service and helps developers make money.More than $116 billion of the App Store’s 2019 sales of almost $140 billion “went entirely into app developers’ back pockets,” Apple said.The case is Epic Games Inc. v. Apple Inc., 20-cv-05640, U.S. District Court, Northern District of California (Oakland).(Updates with Apple’s argument in court filing in third paragraph.)For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.