US senator Elizabeth Warren of Massachusetts and congressman Jerry Nadler of New York have called on government bodies to investigate what they allege is the “predatory pricing” of .com web addresses, the Internet’s prime real estate.

In a letter delivered today to the Department of Justice (DOJ) and the National Telecommunications and Information Administration (NTIA), a branch of the Department of Commerce (DOC) that advises the US President, the two Democrats accuse VeriSign, the company that administers the .com top-level domain, of abusing its market dominance to overcharge customers.

In 2018, under the Donald Trump administration, the NTIA modified the terms on on how much VeriSign could charge for .com domains. The company has since hiked prices by 30 percent, the letter claims, though its service remains identical and could allegedly be provided far more cheaply by others.

“VeriSign is exploiting its monopoly power to charge millions of users excessive prices for registering a .com top-level domain,” the letter claims. “VeriSign hasn’t changed or improved its services; it has simply raised prices because it holds a government-ensured monopoly.”

VeriSign did not respond immediately to a request for comment. But in an August blog post entitled “Setting The Record Straight,” the company claimed that discourse around its management of .com had been “distorted by factual inaccuracies, a misunderstanding of core technical concepts, and misinterpretations regarding pricing, competition, and market dynamics in the domain name industry.”

In the same blog post, the company argues that it is not operating a monopoly because there are 1,200 generic top level domains operated by other entities, including .org, .shop, .ai or .uk.

Though far from a household name, VeriSign takes in about $1.5 billion in revenue each year for servicing its particular section of the Internet’s inscrutable plumbing.

In their letter, Warren and Nadler allege that VeriSign has exploited its exclusive right to charge for highly sought-after .com addresses to juice its revenues and drive up its share price—all at the expense of customers for whom there is no viable alternative.

The letter claims that separate agreements with the NTIA and Internet Corporation for Assigned Names and Numbers (ICANN), a non-profit established by the DOC to oversee the web’s domain name system, have allowed VeriSign to establish monopoly power. The letter also alleges VeriSign might be in violation of the Sherman Act. The former sets how much the company can charge its customers for registering .com addresses, while the latter assigns VeriSign as the “sole operator” of the .com domain.