custom_surcharge WooCommerce

add_action( 'woocommerce_cart_calculate_fees','custom_tax_surcharge_for_retailers', 10, 1 );
function custom_tax_surcharge_for_retailers( $cart ) {
	if ( is_admin() && ! defined('DOING_AJAX') ) return;
	global $woocommerce;

	if ( isset( $_POST['post_data'] ) ) {
		parse_str( $_POST['post_data'], $post_data );
	} else {
		$post_data = $_POST;
	}
	if ( 'AT' == WC()->customer->get_billing_country() OR $post_data['billing_user'] == 'Ιδιώτης' ) { 
		$percent = 20;
		// Calculation
		$surcharge = ( $cart->cart_contents_total + $cart->shipping_total ) * $percent / 100;
		// Add the fee (tax third argument disabled: false)
		$cart->add_fee( __( 'ΦΠΑ', 'woocommerce')." ($percent%)", $surcharge, false );
	}
}

add_action( 'wp_footer', 'woocommerce_fieldchange_bind' );
function woocommerce_fieldchange_bind() {
    if (is_checkout()) {
    ?>
    <script type="text/javascript">
    jQuery( document ).ready(function( $ ) {
        $('#select2-billing_country-container, CHANGEME').click(function(){  //Change CHANGEME to your field's identifier
            jQuery('body').trigger('update_checkout');
        });
    });
    </script>
    <?php
    }
}