Adding Checkbox field to WooCommerce checkout to update billing fields

functions.php

<?php

/**
 * This function assumes that "fedex_is_insured" filter is enabled
 * in WooCommerce Fedex Plugin. This was manually added by me by altering the Fedex plugin code.
 * $this->insure_contents = apply_filters( 'fedex_is_insured', $this->insure_contents);
 */
function nb_update_insurance_for_fedex(){
    $insurance = WC()->session->get( 'nb_insurance' );   
    if ( "1" == $insurance ) {
        return true;
    }
    return false;
}
add_filter( "fedex_is_insured", "nb_update_insurance_for_fedex", 10);


/**
 * Add Insurance Status in summary Tables
 */
// add_action( 'woocommerce_cart_totals_before_shipping', 'nb_display_cart_insurance_status', 20 );
add_action( 'woocommerce_review_order_before_shipping', 'nb_display_cart_insurance_status', 20 );
function nb_display_cart_insurance_status() {
  
    $chosen = WC()->session->get('nb_insurance');
    $chosen =  ("1" == $chosen)  ? "Insurance Added" : "Insurance Not Added";
        echo ' <tr class="insurance-option">
            <th>' . __( "Insurance" ) .'</th>
            <td data-title="total-volume">'.$chosen.'</td>
        </tr>';

}

/**
 * Display Insurance selector checkbox on checkout page
 */
function nb_insurance_checkbox() {
  $chosen = WC()->session->get('nb_insurance');
  $chosen =  ("1" == $chosen)  ? true : false;


   echo '<div id="checkout-insurance">';
   woocommerce_form_field( 'nb_insurance', array(
        'type'          => 'checkbox',
        'label'         => __('Add Insurance.'),
        'required'  => false,
        ), $chosen);
   echo '<p style="padding-left: 17px; font-weight: normal; font-style: italic;">Incredible Underwater LED Lighting, INC is not responsible for any purchase lost/damaged during shipping.</p>';
   echo '</div>';    
}
add_action( 'woocommerce_after_order_notes', 'nb_insurance_checkbox' );

/**
 * Add Javascript for Insurance selector checkbox for pricing refresh
 */
function nb_insurance_cb_cart_refresh() {
if ( ! is_checkout() ) return;
    ?>
    <script type="text/javascript">
    jQuery( function($){
        $('form.checkout').on('change', 'input[name=nb_insurance]', function(e){
            e.preventDefault();
            var p = "false";
            if($(this).prop("checked") == true){
                p = "true";
            }
            jQuery.ajax({
                type: 'POST',
                url: wc_checkout_params.ajax_url,
                data: {
                    'action': 'woo_get_ajax_data',
                    'nb_insurance': p,
                },
                success: function (result) {
                    $('body').trigger('update_checkout');
                }
            });
        });
    });
    </script>
    <?php
}
add_action( 'wp_footer', 'nb_insurance_cb_cart_refresh' );

/**
 * Save Insurance Setting in Server
 */
function nb_insurance_cb_set_session() {
   $cb = esc_attr($_POST['nb_insurance']);
    if ("true" == $cb ){
        WC()->session->set('nb_insurance', "1" );
    }
    else{
        WC()->session->set('nb_insurance', "0" );
    }

    echo json_encode( WC()->session->get('nb_insurance'));
    die();
}
add_action( 'wp_ajax_woo_get_ajax_data', 'nb_insurance_cb_set_session' );
add_action( 'wp_ajax_nopriv_woo_get_ajax_data', 'nb_insurance_cb_set_session' );