Nobody likes to receive a prank telephone call. The only thing that makes that even worse is when we can't figure out who is behind the irritation. Pranks are the ones that come in at all hours of the night with nobody on the other end of the line, or with lame jokes "is your refrigerator running?" or asking for artificial names "I.P. Freely" à-la Bart Simpson to Moe the bartender.
If you only have this happen once, it's usually a bother, but it can be shrugged off and forgotten over time. However, if the prankster is making a regular bother of him or herself, it may be time for you to take matters into your own hand and find out who it is, and how to make it stop.
Begin by recognizing whether you're receiving prank calls or if you're being harassed and threatened. The reason for taking this step is that if you feel that you, your family, or your property is in any danger from the individual (for example, if the person has actually claimed that he or she will harm you or someone you know, or destroy something you own), then this is actually an illegal action. You should always take these calls seriously, and report them to the police. They will take care of it as they have the right tools and authority to find out who the person is, and stop them right away.
If you are just dealing with a pest, then you will be able to use your own resources to discover who is behind it and make them stop. If you can find out the telephone number of the irritant, by using Caller ID or a *69 service (both of which come with a fee that you will want to investigate before using), then you can go online and use a Reverse Phone Search to find the name and address behind the digits.
With this information, if you know the individual, you may simply be able to call them up and calmly ask that they stop now that you know who they are - in the case of a child, you may want to make this calm request to the parents who can then enforce the request. If you don't know the person, or if you don't feel that contacting them will help, you can contact their phone service provider (or yours) and report the activity so that they can take action and - if necessary - cut their service.