The U.S. Federal Communications Commission today proposed a record $300 million fine against an auto warranty robocall operation that made billions of calls to more than 550 million phones across the states -United.

This operation had been run by Michael Aaron Jones and Roy Cox, Jr. since at least 2018, and it was the largest robocall operation ever investigated by the FCC.

Their robo-call lead generation system was designed to sell vehicle maintenance contracts deceptively marketed as car warranties in phone calls described by those on the other end of the line as “relentless” and “bullying”.

These robocalls also reached healthcare workers during the COVID pandemic and spoofed hospital phone numbers, causing people who received them to call back and block hospital phone lines.

“This robocall system made more than 5 billion robocalls to more than half a billion phone numbers in a three-month period in 2021, using pre-recorded voice calls to prompt consumers to speak to a “warranty specialist” about extending or reinstating their car warranty,” the FCC said.

“The FCC Enforcement Bureau investigation found that the Cox/Jones company apparently made approximately 5,187,677,000 calls to 550,138,650 wireless and home phones from January through March 2021, using 1,051,461 identification numbers unique callers – enough calls to have called every person in the United States 15 times in those three months alone.”

Today’s announcement follows previous action taken by the FCC in July when the federal government agency ordered 8 US-based voice service providers (Call Pipe, Fugle Telecom, Geist Telecom, Global Lynks, Mobi Telecom, South Dakota Telecom, SipKonnect and Virtual Telecom) to stop offering their services to the operation behind these auto guaranteed scam robocalls within 48 hours.

As a result, the volume of robocalls related to the car warranty scam dropped by 99%, according to communication company Robokiller.

In total, the number of auto warranty robocalls fell from nearly 1 billion in June to less than 7 million in September, representing just 1% of all robocalls, a sharp drop from 17% previous ones.

Today’s proposal follows a May 2020 FCC order saying so no longer warn caller bots before fining them for breaking the law and harassing American consumers.

The same order increased the maximum penalty for each intentional illegal robocall to $10,000 and extended the time in which robocallers can be fined to four years for violating FCC rules.

FCC’s fight against malicious robocalls was driven by a call to action issued by attorneys general of 35 states in 2018who called on the agency to end the rising tide of robocalls people are receiving on mobile and landline devices across the country.

“Today’s proposed fine is the largest such action in FCC history, in large part because the FCC found that robocallers met the agency’s criteria for gross violations and deserved therefore a significantly increased proposed fine,” the FCC added on Wednesday.