A fraud prevention system has a customer sign-up program accessible via a computer network which functions to receive an inquiry from a customer referred by an affiliate, provide a customer sign-up page, and receive sign-up information from the customer, including a phone number. A validation program confirms that the phone number is valid by referencing a phone number database, generates a validation page having a PIN, calls the phone number, receiving an inputted PIN, confirms that the inputted PIN matches the PIN of the validation page, updates the phone number database so that the phone number is no longer valid, and provides credit to the affiliate.