This was just published today about a telephone scam:
In recent weeks, U.S. Citizenship and Immigration Services (USCIS) learned of a new telephone scam targeting USCIS applicants and petitioners. Scammers are using a technique called “Caller ID spoofing" to display a misleading or inaccurate phone number in a recipient’s Caller ID. The scammer poses as a USCIS official and requests personal information (such as Social Security number, passport number, or A-number), identifies supposed issues in the recipient’s immigration records, and asks for payment to correct these records.
If you receive a call like that, USCIS urges you to say “No, thank you" and hang up immediately.
USCIS never asks for any form of payment or personal information over the phone. Do not give payment or personal information over the phone to anyone who claims to be a USCIS official. In general, we encourage you to protect your personal information and not to provide details about your immigration application in any public area.
If you have been a victim of this telephone scam, please report it to the Federal Trade Commission at https://www.ftccomplaintassistant.gov/, or report it to an appropriate state authority. (Visit www.uscis.gov/avoidscams for information on where to report scams in your state.)
If you have a question about your immigration record, please call the National Customer Service Center at 1-800-375-5283, or make an InfoPass appointment by visiting our website at http://infopass.uscis.gov/.