Vat id not display on admin

replace VAT_cui with billing_VAT_cui on both occurences in woocommerce-vat.php

diff --git a/woocommerce-vat.php b/woocommerce-vat.php
index f6521c0..2829864 100644
--- a/woocommerce-vat.php
+++ b/woocommerce-vat.php
@@ -50,7 +50,7 @@ class WoocommerceCustomCheckoutVATField {

 		// Our hooked in function - $fields is passed via the filter!
 	public function VAT_override_checkout_fields( $fields ) {
-				$fields['billing']['VAT_cui'] = array(
+				$fields['billing']['billing_VAT_cui'] = array(
 				'label'     => __('VAT', 'woocommerce'),
 				'placeholder'   => _x('VAT', 'placeholder', 'woocommerce'),
 				'required'  => true,
@@ -64,7 +64,7 @@ class WoocommerceCustomCheckoutVATField {
 	public function VAT_custom_checkout_field_order_meta_keys( $order ) {
 		echo "<p><strong>VAT:</strong>" .
 		//$order->order_custom_fields['_VAT_cui'][0] . "</p>";
-		 get_post_meta( $order->id, '_VAT_cui', true ) . "</p>";
+		 get_post_meta( $order->id, '_billing_VAT_cui', true ) . "</p>";

 }