A computer implemented method and system is provided for managing false answer supervision (FAS) in a telephony network. A call record recording multiple call events occurring at a terminal gateway is accessed. FAS events originating at the terminal gateway are detected. Suspect illegitimate call events are analyzed based on a combination of conditions. The suspect illegitimate call events are filtered for detecting events suspected of FAS. The FAS events are confirmed after discounting the suspected FAS events based on whether a proportion of the suspected FAS events is within a FAS threshold. A statistical inference of current behavior and past behavior of the terminal gateway is inferred. Threshold values are established for acceptable number of FAS events. A non-compliant behavior of the terminal gateway is inferred when the FAS events exceed the established threshold values. A service provider associated with the terminal gateway is notified for remedying the non-compliant behavior.