public function rejectCall($to, $id, $callId)
    {
        $rejectNode = new ProtocolNode('reject',
            [
              'call-id' => $callId,
            ], null, null);

        $callNode = new ProtocolNode('call',
            [
              'id' => $id,
              'to' => $this->getJID($to),
            ], [$rejectNode], null);

        $this->sendNode($callNode);
    }