function sb_cf7_catname( $atts) {
    // Only in thankyou "Order-received" page
    global $wp;



    // Get the order ID
    $order_id  = absint( $wp->query_vars['order-received'] );


    if ( empty($order_id) || $order_id == 0 )
        return; // Exit;

    // Testing output (always use return with a shortcode)
    return 'Numer zamówienia: ' . $order_id . ' ';

}
add_shortcode( 'SB_CF7_CATNAME', 'sb_cf7_catname');