Calls from a phone identified as being a source of harassing or other undesirable phone calls are blocked at a mobile positioning center (MPC). Upon request by the PSAP, a call record detail can be obtained from the MPC revealing a simulated “callback phone number” as well as a unique number identifier of the phone, such as an ESN or MEID. The MPC then intercepts all future incoming calls from phones with that unique identifier number and routes them to a recording that advises the harasser that the phone has been identified as a harasser and is now blocked. The recording can also advise the caller how to restore service. In a preferred embodiment, the MPC sets a timer to automatically restore service after a designated length of time.