WooCommerce Smart COD

The plugin URL: https://wordpress.org/plugins/wc-smart-cod/

In file functions.php of your current wordpress theme add next code:

add_filter('wc_smart_cod_fee', function($fee, $settings) {
    if (class_exists('WOOCS') AND $fee) {
        global $WOOCS;
        if ($WOOCS->is_multiple_allowed) {
            $currrent = $WOOCS->current_currency;
            if ($currrent != $WOOCS->default_currency) {
                $currencies = $WOOCS->get_currencies();
                $rate = $currencies[$currrent]['rate'];
                $fee = $fee * $rate;
            }
        }
    }
    return $fee;
}, 2, 100);

Shortcodes, functions, actions and filters reference for FOX WooCommerce Currency Switcher