With a little detective work, it's possible to find out who provides cell phone service to a particular phone number. Use the information to determine the parent company of a prepaid service, or to see whether a number is actually linked to a cell phone (as opposed to a land line).
Watch your caller ID when the person calls. Write down all 10 digits of the phone number that appears on the screen.
Access an online telephone directory. Type the first seven digits of the number in the search field, then click "Search by Number."
Read the result listed as "Telephone Company" on the web page that appears. This is the caller's cell phone service provider.