Visa’s heft in the market has allowed it to pressure merchants into accepting its cards to avoid steep costs on billions of dollars of transactions, the DOJ says.

The Department of Justice (DOJ) filed an antitrust lawsuit against Visa. The lawsuit alleges that the financial firm holds a monopoly over debit network markets allowing it to charge banks and markets with exorbitant fees that get passed onto consumers and keep rival companies like PayPal and Square from competing on their level.

The complaint says Visa penalizes merchants and banks who don't use its own payment processing tech to process debit transactions.