As of 2015 the National Customer Service Center of U.S. Citizenship and Immigration Services, or USCIS, answers immigration questions by phone at (800)375-5283. Representatives are available by phone during normal business hours, and automated answers to many common questions are available around the clock, according to the USCIS.
Automated services available by calling the USCIS include basic information regarding immigration eligibility, what's required to file an immigration application, status of an application, and local field office locations and hours. Customers who have questions or who need help with their immigration applications get assistance by calling during business hours. A customer calling about his application needs to have the receipt number, A-number or tracking number available during the call, says the USCIS website.