UPS Shipping Method by WooCommerce

Plugin URL: https://woocommerce.com/products/ups-shipping-method/

to your current child wp theme file functions.php add next code:

add_filter('woocommerce_shipping_ups_check_store_currency', function ($alow, $currency, $xml, $_this) {
    return false;
}, 99, 4);

add_filter('woocommerce_shipping_ups_rate', function ($data, $currency, $xml, $_this) {

    if (class_exists('WOOCS')) {
        global $WOOCS;
        if ($WOOCS->is_multiple_allowed) {
            $current = $WOOCS->current_currency;
            $currencies = $WOOCS->get_currencies();
            $def_currency = $WOOCS->default_currency;
            if ($current != $currency && isset($currencies[$currency])) {
                $rate = $currencies[$currency]['rate'];
                $data['cost'] = $data['cost'] / $rate;
                $data['cost'] = $WOOCS->woocs_exchange_value(floatval($data['cost']));
            }
        }
    }

    return $data;
}, 99, 4);

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