Abstract: A system for monitoring phone numbers includes a computing device having at least one processor and memory associated with the processor. A telephone network supports a plurality of telephone numbers. For each of the phone numbers, the computing device is configured to detect call activity involving the phone number during a detection period having a preselected duration, determine an answer seizure ratio (ASR) for the phone number during the detection period from the call activity, determine a difference between the ASR during the detection period and an ASR from at least one previous detection period for the phone number, and determine whether the difference satisfies at least one preselected criterion. When the criterion is satisfied, the computing device instigates a procedure to investigate or repair the phone number.