Phone harassment is a fairly general term used to describe repeated, unwanted calls that cause grief, distress or invasion of your personal privacy. Abusive or threatening calls are a criminal offence in some states and should be immediately reported to the police. Any one phone call can be considered harassment, but a local phone company will usually not take complaints unless there have been numerous transgressions. There are several steps you can take to avoid phone harassment, including putting your home telephone number on the "do not call list" for telemarketers. Your mobile phone can also be placed on this list as well.
Find out your phone company's policy regarding reporting phone harassment. Some companies mandate that you file a formal complaint with local police first; others recommend that you call the phone company's complaint department before speaking to police.
Keep notes on harassing calls that have been made to your phone number numerous times. Write down what was said and when the call came in. You may need this as evidence later.
Report repeated harassing calls to either the phone company or local police, according to your phone company's policy. Extremely malicious calls or calls with direct threats of violence should be immediately reported to the police. Use the notes you recorded on the harassing calls as evidence when giving police a statement.
Have a "trap" installed on your phone line---if you do not have caller ID or the feature doesn't indicate where the call is coming from---by your phone company for particularly frequent harassing calls or extremely threatening calls. This "trap" will allow the call to be traced, and will help local police apprehend the perpetrator. A more advanced version of a trap can be installed also, using a service called "Call Trace."
Screening calls from unknown numbers, and placing your number on the "do not call list" for telemarketers in your region are ways to avoid harassing calls.