The U.S. Justice Department on Tuesday sued Visa, the world’s biggest payments network, saying it propped up an illegal monopoly over debit payments by imposing “exclusionary” agreements on partners and smothering upstart firms.

The Justice Department is accusing Visa of running a debit card monopoly that has hiked fees for American consumers and businesses.

The U.S. Justice Department has filed an antitrust lawsuit against Visa, alleging that the financial services behemoth uses its size and dominance to stifle competition in the debit card market