AT&T says it blocks or labels 1 billion robocalls per month.
The telecom giant says it has ramped up its spam-swatting efforts, blocking fraud calls from ever reaching customers' phones, and labeling suspected spam so customers can choose to answer or not.
The company says evidence it gathered resulted in at least seven federal enforcement actions against phone scammers last year.
AT&T's "call protect" blocking and labeling system is automatic for wireless customers.
Digital home phone users can opt-in to "digital phone call protect", but that requires activation by the customer in their account settings.