HARTFORD, Conn. (WTNH) — Connecticut Attorney General William Tong is urging the Federal Communication Commission to close loopholes that allow scammers to robocall Americans, according to an announcement Tuesday morning.

“Anti-robocall technology works, but only if everyone uses it,” Tong wrote.

Tong, along with 50 other state attorney generals, signed a letter to the FCC to ask for an expansion of anti-robocall protections, which include requiring that all telephone providers that route calls to use “more rigorous measures” to prevent robocalls.

The Anti-Robocall Litigation Task Force issued 20 civil investigative demands in August to 20 providers Tong believes routes most of the foreign robocall traffic into the U.S., according to the announcement.

“If these providers are unwilling to adopt these rigorous measures on their own, the FCC must mandate it,” he wrote.

Robocalls cost the nation about $13.5 billion a year, according to Tong, who noted that most are from foreign scammers who spoof U.S. phone numbers to trick their victims into thinking they’re answering a call from a local number. The proposed rules would extend to phone companies that “are exclusively responsible” for the calls.

The program, STIR/SHAKEN, is a caller ID system that helps block spoofed calls. However, only providers that originate call traffic are required to use it.

“If all telecom companies have the same robocall mitigation practices, bad actors will not be able to exploit inconsistencies among providers and law enforcement will be better able to identify and prosecute the bad actors who try profit from illegal robocalls,” the announcement reads.

The 16-page letter also requests that these “gateway providers” must be required to respond to traceback requests from the FCC and law enforcement within 24 hours of receiving one.

“As with other specific measures adopted in the past, State AGs recognize that the Commission’s proposed actions, including mandatory call blocking, will not completely eradicate the illegal robocall epidemic,” the letter reads. “However, we are confident that the proposals under consideration will help bring bad actors to account.”