Add extra charges for cash on delivery.

gistfile1.txt

class My_Wc_Cart
{
	protected $logger;
  
	public function __construct()
	{
		$this->logger = new WC_Logger();
		add_action('woocommerce_cart_calculate_fees', [$this, 'check_fees'], 10, 1);
	}

	public function check_fees($cart)
	{
		// Add extra charges for cash on delivery.
		if (isset($_POST['payment_method']) and $_POST['payment_method'] === 'cod' ) {
			$cart->add_fee('cod-fee', 100, false, '');
		}
	}
}