Add Billing and Additonal info header in WC checkout

fucntions.php

add_action( 'woocommerce_before_checkout_billing_form', 'dt_wc_billing_header', 10 );

function dt_wc_billing_header() {

	if ( wc_ship_to_billing_address_only() && WC()->cart->needs_shipping() ) : ?>

		<h3><?php esc_html_e( 'Billing &amp; Shipping', 'woocommerce' ); ?></h3>

	<?php else : ?>

		<h3><?php esc_html_e( 'Billing details', 'woocommerce' ); ?></h3>

	<?php endif;
}


add_action( 'woocommerce_before_order_notes', 'dt_wc_additonal_header', 10 );

function dt_wc_additonal_header() {
	?>

			<h3><?php esc_html_e( 'Additional information', 'woocommerce' ); ?></h3>

	<?php 
}