Code-Snippets-Functions/Execute a function on a child site/WooCommerce/update-order-field-value-after-order.txt

add_action( 'woocommerce_thankyou', 'wc_alter_checkout_fields_after_order' );
 
function wc_alter_checkout_fields_after_order( $order_id ) {
   $order = wc_get_order( $order_id );
   $phone = $order->get_billing_phone();
   $calling_code = WC()->countries->get_country_calling_code( $order->get_billing_country() );
   $calling_code = is_array( $calling_code ) ? $calling_code[0] : $calling_code;
   if ( $phone && $calling_code && ! str_starts_with( $phone, $calling_code ) ) {
      // str_starts_with() works on PHP 8+ only
      $phone = $calling_code . $phone;
      update_post_meta( $order_id, '_billing_phone', $phone );   
   }   
}