There are probably few people who appreciate prank calls. Unfortunately, many have to deal with immature pranksters calling their numbers to joke around or even make threats. Prank callers often block their caller I.D.s, making it much harder for victims to track them down. However, there are ways to find a prankster's number, including the star-69 dial option, adding a call trace to your number and having your phone company "trap" the number.
Dial "69" immediately after the prankster calls to get his number. This option reveals the last person who dialled your number. Make sure not to wait long after the call, as another call might nullify this. The star symbol () is at the bottom left of a standard number pad.
Add on your phone company's "call trace" option for an extra fee. Dial "*57" after the prankster calls to trace the number. Dial "1157" if you are using a rotary phone. Your company then hands over the number to the authorities. Keep in mind that if the caller is making dangerous threats against you, you should call the authorities anyway. Do not take the law into your own hands.
Ask your phone company to place a "trap" on your phone line. Give your provider your contact information, telephone number, description of the harassing or threatening calls and a log of times and dates the person calls. The trap will immediately trace the prankster's number after he calls and your company will get in contact with the authorities, giving them the number.