public function requestShipmentRefund($shipment_id, $email, $options)
    {
        $content = [
            'email' => $email,
        ];

        $xml = Array2XML::createXML(
            'non-contract-shipment-refund-request',
            $content
        );
        $envelope = $xml->documentElement;
        $envelope->setAttribute(
            'xmlns',
            'http://www.canadapost.ca/ws/shipment-v8'
        );
        $payload = $xml->saveXML();

        $endpoint = sprintf(
            'rs/%s/%s/shipment/%s/refund',
            $this->config['customer_number'],
            $this->config['customer_number'],
            $shipment_id
        );
        $response = $this->post(
            $endpoint,
            [
                'Content-Type' => 'application/vnd.cpc.shipment-v8+xml',
                'Accept' => 'application/vnd.cpc.shipment-v8+xml',
            ],
            $payload,
            $options
        );
        return $response;
    }