A device is configured to detect congestion and throttle phone calls in a telephone communication system. The device receives, from a telephone dialing system, an indication indicating that a call to a phone number has successfully ended. In response to the indication, the device determines that a set of initial digits of the phone number matches a flooding group number of a flooding group, where the flooding group has a capacity limit. The device determines that a maximum number of concurrent active calls for the flooding group during a predefined period of time is within a predetermined threshold from the capacity limit of the flooding group and that no failed calls have occurred for the flooding group during the predefined period of time. In response to the determining, the device increases the capacity limit of the flooding group.