If the phone company in your market has created an area code split, you will want to use this procedure to convert the exchanges from the OLD area code to the NEW area code.
Area Code Conversion screen
First, you will need a list of all prefixes in the Old Area Code that will be changing. This should be readily available from your local phone company. Many times these pending prefix changes are listed at the front of the local white pages directories. They are often available at the local phone companies web site, or through some long distance carrier's web sites.
Simply enter all the affected prefixes that will be changing. The prefix is the three numbers after the area code. For example, consider the number 619-659-3600. The prefix in this case is 659. Once you have entered all the area code/prefix combinations that are changing, you must enter the NEW area code at the bottom of the screen. Click Run Conversion Now and any numbers that are in the Old area code will be converted to the New area code!