How do I Find What Phone Company a Number Belongs to?by David Sarokin
The North American Numbering Plan Administration, NANPA, is the group responsible for assigning blocks of telephone numbers to individual telephone companies. You can download a table of the actual assignments at the NANPA website. Another website, Telcodata.us, provides a simple look-up service. Either way, matching a phone number to the telephone company that owns it is a straightforward process.
Visit the Telcodata.us website.
Click on the "Area/Exchange" link under "Common Lookups."
Enter the area code and exchange (first three local numbers) of the telephone number you are searching. Click "Search." Telecodata.us will display the name of the company assigned to that area code and exchange.
Visit the NANPA "Central Office Code Assignment Records" website to download regional lists of area code/exchange assignments to telephone companies.
Select the NANPA region of the country of interest to you, and click on the "download" link to open up a text file with the master list of company assignments for the region. The text file is zipped (compressed). Most computers will automatically unzip the file without any need for user action.