According to the Consumer Fraud Reporting website (consumerfraudreporting.org), a harassing call exhibits the characteristics of repeated calling and hanging up, repeated calling and remaining silent, threatening language, heavy breathing or playing a message. Nearly every state considers such calls illegal, whether the calls are from a business or from an individual. You should always take immediate action and document the calls, reporting them to your phone company and local police station.
Keep a record of the calls. Write down the date, time and duration of the call. Make note of the speaker's gender, type of voice, everything the speaker said, any accents or speech impediments, approximate age, background noise, and whether or not a number appeared on your caller ID.
Contact your local police department. While your phone company will block the caller from your line regardless of whether or not you file a police report, it's always better to make a formal record, particularly if the problem escalates.
Ask your phone company to put a "trap" line on your phone. This service is free and allows your phone company to retrieve the number of the business. The phone company will usually ask you to continue to keep a log of the calls for two more weeks once the trap line is in place.
Consider using a "call trace" service. This service isn't free, but it allows you to trace calls immediately. First your phone company has to set this service up on your phone in advance; then, after you receive a harassing call, you press "*57," which traces the number immediately.
Contact the National Do Not Call Registry at (888) 382-1222 and ask to be put on its roster of protected people. This prohibits telemarketers and other business representatives from harassing you.
Many states have "Do Not Call" lists. Get in touch with your state's Office of Consumer Protection to see if your state has such a list. If it does, ask to be placed on it.