On the heels of recent fines for unauthorized operations and a wireless crimes investigation, the Federal Communications Commission (FCC) announced last week yet another hit to AT&T: a $25 million settlement for failing to police its call centers. According to The New York Times, employees at the carrier’s contracted call centers collected subscriber information, including Social Security numbers, and sold the valuable data to unidentified third parties.

After learning of the breach, AT&T self-reported the problem to both the California attorney general and the FCC, and it cut ties with at least one Mexico-based call center. This mea culpa was not enough for AT&T to garner mercy from the FCC.

The $25 million settlement is the largest data breach fine ever imposed by the agency. As FCC Chairman Tom Wheeler said, “The commission cannot — and will not — stand idly by when a carrier’s lax data-security practices expose the personal information of hundreds of thousands.”

For more, read The New York Times recent story on the settlement.