A telephone prefix, also called a "telephone exchange," makes up the second set of three numbers in a 10-digit phone number. For example, "555" is the prefix in the mock telephone number 202-555-1234. If the city you would like to know the telephone prefix for is local, that city's telephone prefix numbers will be in the introductory pages of the White Pages phone book. You can look up the prefix numbers there, or online. If the city you would like to know the telephone prefix for is non-local, you'll have to look up the prefix numbers online or by visiting a library.
Get the White Pages phone book. If the city you want to find the telephone prefix for is non-local you won't be able to use the phone that was delivered to your house to look up the telephone prefix. You should check with your local library. Your local library may have White Page phone books from other cities in their catalog.
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Flip to the "Area Code" section of the phone book. This section is located in the book's introductory pages.
Look up the city's "Area Code."
Go to the "Area Code / Exchange" code section of the phone book. This section is also located in the book's introductory pages.
Find the area code(s) assigned to the city to see a list of all the telephone prefixes used in that area code.
Go to Verizon's "Area Code Lookup" website (see the link in the Resources).
Click on the "or select a state" drop-down menu. Scroll through the list of states to find the one the city is located in. Click on it to select it. Click the little arrow next to the "or select a state" drop-down menu to submit your query.
Scroll down the page to see the list of all the major cities located within the selected state, along with its corresponding area code(s). Make a note of the city's area code(s). If the town you're looking for is not in the list (probably because it's a small town), it's safe to assume that that town shares the same area code as its closest major city.
Go to the "Phone Number Browsing" page on the White Pages website (see the link in the Resources). Click on whatever hundreds group your city's area code belongs to in the "US Area Codes" section of the Web page.
Locate and click on the city's area code. This will bring up a list of all the telephone prefixes used in the selected area code. In addition, you'll also see what line type the prefix is used for (cell phone or landline), and the telephone carrier the exchange is assigned to (such as "Verizon" or "New Cingular Wireless").