I want to add 300 to order total on woocommerce checkout page but woocommerce_calculate_totals hook doesn\'t do the job...
If I use var_dump($total), I see the corre
Since Woocommerce 3.2, the hook
woocommerce_calculate_totalsdoesn't work for that.
See explanations on this thread: Change Cart total price in WooCommerce
You will have to use one of the following ways using:
1) The filter hook woocommerce_calculated_total this way:
add_filter( 'woocommerce_calculated_total', 'change_calculated_total', 10, 2 );
function change_calculated_total( $total, $cart ) {
    return $total + 300;
}
2) The Fee API like:
add_action( 'woocommerce_cart_calculate_fees', 'add_custom_fee', 10, 1 );
function add_custom_fee ( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;
    $fee = 300;
    $cart->add_fee( __( 'Fee', 'woocommerce' ) , $fee, false );
}
Code goes in function.php file of your active child theme (or active theme) or also in any plugin file.