Then contact your local police department and ask a detective to open a case investigating the annoying or threatening calls. The phone company will give the detective the numbers of the calls you traced. This is technologically the most accurate way of documenting annoyance calls. In Rhode Island, this is still a free and legal way to help the authorities prosecute an annoyance caller. Many abusers know how to block their calls, and it can be expensive for people who are being harassed or threatened to add Caller ID to their monthly phone costs and purchase a Caller ID box.
Some phone companies offer reverse directory services.
Reverse directories are often available at local libraries.