Amazon knew millions of customers were unintentionally signing up for Prime membership but did not stop them because doing so would have hurt its revenue, U.S. Federal Trade Commission attorneys argued Tuesday at the start of an anti-trust case.

Amazon is on trial in Seattle after the FTC accused the retailer of tricking customers into Prime memberships and making cancellations difficult.

A jury will decide if Amazon tricked its customers into signing up for Prime and made it difficult to cancel the subscription service, as the FTC alleges.