SEE:
https://egov.uscis.gov/e-Request/Intro.do
e-Request
e-Request is a web-based tool that allows you to place an inquiry with USCIS for certain applications and petitions. Currently you may make an inquiry on an N-400 or I-90 that is beyond posted processing times or on an I-90 where you did not receive an Application Support Center (ASC) appointment notice.
To place an inquiry, you will need your receipt number. If you do not have your receipt number contact the USCIS Customer Service at 1-800-375-5283 or 1-800-767-1833 (TTY).
If you have previously initiated a service request, please wait 30 days to receive a response before notifying USCIS again.
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You had already submitted a servcie request yourself online. For the applications and petitions for which this is not an option, such a "service request" is made over the phone. Whether it is you online or a customer service rep via 1-800#, the same sytem records the request and directs it to the USCIS Office handling the case for a person to look into the matter and report findings.