The US Department of Justice has sued Visa, alleging that the company has maintained an illegal monopoly over debit payments, resulting in American consumers and merchants paying billions of dollars in additional fees. Visa has denied the allegations, stating that the lawsuit ignores the reality of competition in the debit space. The DOJ claims that Visa's exclusionary agreements and practices have smothered upstart firms and limited innovation. The lawsuit seeks to prevent Visa from engaging in anticompetitive practices.