http://www.rfc-editor.org/rfc/rfc8197.txt
RFC 8197: A SIP Response Code for Unwanted Calls, H. Schulzrinne2017-07-01T23:00:00-00:00This document defines the 607 (Unwanted) SIP response code, allowing called parties to indicate that the call or message was unwanted. SIP entities may use this information to adjust how future calls from this calling party are handled for the called party or more broadly.