On June 28, U.S. Citizenship and Immigration Services launched a new self-service tool allowing benefit requestors, and their attorneys and accredited representatives, to reschedule most biometric services appointments before the date of the appointment.
New tool provides option to reschedule a biometric services appointment online without calling the USCIS Contact Center
USCIS only accepts untimely rescheduling requests made to the USCIS Contact Center and does not accept untimely requests to reschedule by mail or in-person at a USCIS office or through the myUSCIS online rescheduling tool.
Individuals should have USCIS online account to use the tool. The new tool can be used for both paper and on-line filed requests.
For more info; refer: Link
Source: USCIS NEWS RELEASES