Spotify is ramping up its fight with Apple over app store regulations it says have impacted the launch of its new audiobooks business. 

The streaming giant says that Apple will not allow Spotify to explain to users where and how to buy an audiobook or list the cost of the book and will not let the company send emails directing users to purchase the book. Spotify launched its audiobooks business in late September. 

“With our Audiobooks launch, Apple has once again proven just how brazen it is willing to be with its App Store rules, constantly shifting the goalposts to disadvantage their competitors,” Spotify CEO Daniel Ek said in a statement. 

If Spotify allowed users to buy the audiobook directly within the app, it would have to give 30 percent of the revenue to Apple. So instead, the company developed a workaround system for users to buy the audiobook on its website. Spotify is now frustrated with the restrictions Apple is placing around how it can inform customers to make the purchase. 

Spotify said it had hired lawyers to make sure it stayed within the app store guidelines when developing the update to the app. Still, Spotify CEO Daniel Ek said on the company’s earnings call Tuesday that the new app has been rejected by Apple “three or four times.” 

“We have no issue with reader apps adding audiobook content to their apps, linking users out to websites to sign up for services, or communicating with customers externally about alternative purchase options. The Spotify app was rejected for not following the guidelines regarding including explicit in-app communications to direct users outside the app to make digital purchases. We provided them with clear guidance on how to resolve the issue, and approved their app after they made changes that brought it into compliance,” Apple said in a statement.

Audiobooks are available on the app but when an i0S user tries to hit play next to the title, a pop-up appears stating, “Want to listen? You can’t buy audiobooks in the app. We know, it’s not ideal,” without offering further information. On an Android phone, users click the button and receive an email directing them to make the purchase.

In response to Apple’s restrictions, Spotify published a blog post on its site about the issue, spoke out in the press and during the company earnings call and spoke out on its website called “Time to Play Fair,” detailing its allegations against Apple.  

Spotify views Apple as a competitor due to its rival streaming service, Apple Music, which offers music as well as audiobooks. However, Spotify’s fight with Apple dates back several years and also includes the restrictions it places on apps in its stores, including requiring companies to use Apple’s payment system. 

“Almost four years. That’s how long it’s been since Spotify filed a complaint against Apple with the European Commission, and we are still waiting on a decision. And while we wait, Apple continues to dictate what online innovation looks like, doing serious harm to the internet economy, choking competition and the imagination of app developers,” Ek’s statement reads. 

Asked on the earnings call about his outspoken stance toward Apple, Ek said he believes it’s “frankly absurd” that his complaint from several years ago has not been resolved and declared this all part of “the next great battle” for platform neutrality. 

“We want to have the ability to communicate with our customers the way we choose to do that and the way our customers are accepting to have that line of communication. We do not want a gatekeeper or monopoly in the way to dictate how we communicate with our customers,” Ek said on the call.