Threatening telephone calls, especially those that imply violence, are serious incidents that should be reported to the police immediately. Learning how to respond effectively when you receive a threatening or abusive telephone call will protect you from violence and reduce the number of malicious calls you receive.
Threatening telephone calls, which should be distinguished from simple prank calls, may originate from a psychologically unstable person. As such, these calls are often motivated by a desire to both disturb the victim and maintain some kind of control over her. As the receiver of the call, you must immediately make clear that you will not allow the caller to have any control over you. As soon as any derogatory or threatening words are spoken, hang up. If the caller calls back, hang up again. Don't allow him to think that he has the right to speak to you in that way. You gain nothing by engaging the caller after he has threatened you and, in fact, may only inadvertently encourage him to continue harassing you.
As soon as you have hung up on the caller, pick up the phone. When you hear the dial tone, dial "1471" or the number your telephone provider has set aside to trace numbers. Once activated, the system will monitor your incoming calls and you can find the last number to call you. This won't work if the abusive caller masked his caller ID, but it's worth trying before you contact the police.
After you have received a threatening call, report the incident to the police. The phone company will provide all records of the call to the investigating officers. Depending on the seriousness of the threats, the police may pursue the caller immediately or continue to monitor the situation.