An intermediary, rather than the person, rejected the call as unwanted, for example a call blocking or analytics service. It can include a contact for the caller to seek redress if the block is wrong.
Paste a full SIP or Asterisk log into the decoder and ladder tools to see exactly where this response appears in the call and what led to it. Everything runs in your browser, so your logs never leave your device.
Open the SIP decoder See how a SIP call flows