The Federal Trade Commission has sued Amazon, accusing the e-commerce giant of using “dark patterns” to trick people into Prime subscriptions and making it difficult to cancel.

Amazon Prime may be a popular subscription service that offers better deals, faster shipping, and a video subscription service, but the FTC says many customers were tricked into subscriptions they didn’t want. To make matters worse, Amazon allegedly made it difficult for customers to cancel once subscribed.

In a complaint filed today, the FTC charges that Amazon has knowingly duped millions of consumers into unknowingly enrolling in Amazon Prime. Specifically, Amazon used manipulative, coercive, or deceptive user-interface designs known as “dark patterns” to trick consumers into enrolling in automatically-renewing Prime subscriptions.

Amazon also knowingly complicated the cancellation process for Prime subscribers who sought to end their membership. The primary purpose of its Prime cancellation process was not to enable subscribers to cancel, but to stop them. Amazon leadership slowed or rejected changes that would’ve made it easier for users to cancel Prime because those changes adversely affected Amazon’s bottom line.

“Amazon tricked and trapped people into recurring subscriptions without their consent, not only frustrating users but also costing them significant money,” said FTC Chair Lina M. Khan. “These manipulative tactics harm consumers and law-abiding businesses alike. The FTC will continue to vigorously protect Americans from “dark patterns” and other unfair or deceptive practices in digital markets.”

This isn’t the first time the FTC has gone after a high-profile company for using dark patterns to trick users. The agency recently fined Epic Games $520 million for such practices. The fine included $245 million in refunds for dark pattern purchases.