public function update($body) {
        $data = Values::of(array('Body' => $body, ));

        $payload = $this->version->update(
            'POST',
            $this->uri,
            array(),
            $data
        );

        return new MessageInstance(
            $this->version,
            $payload,
            $this->solution['accountSid'],
            $this->solution['sid']
        );
    }