if ( isset( $this->options['wc_notify_customer_payment_successful_enable'] ) ) {
    add_action( 'woocommerce_order_status_processing', array( &$this, 'successful_payment_notification_client' ) );
}


/*
 * WooCommerce Successful payment notification client
 *
 * @param $checkout
 */
public function successful_payment_notification_client ( $order_id ) {
    // Check the mobile field is empty
    if ( empty( $_REQUEST['mobile'] ) ) {
        return;
    }

    $args = array(
        'post_id' => $order_id,
        'orderby' => 'comment_ID',
        'order'   => 'DESC',
        'approve' => 'approve',
        'type'    => 'order_note',
        'number'  => 1
    );

    remove_filter( 'comments_clauses', array( 'WC_Comments', 'exclude_order_comments' ), 10, 1 );

    $notes = get_comments( $args );

    add_filter( 'comments_clauses', array( 'WC_Comments', 'exclude_order_comments' ), 10, 1 );

    $order          = new WC_Order( $order_id );
    $this->sms->to  = array( $_REQUEST['mobile'] );
    $template_vars  = array(
        '%order_id%'           => $order_id,
        '%order_number%'       => $order->get_order_number(),
        '%status%'             => $order->get_status(),
        '%billing_first_name%' => $_REQUEST['billing_first_name'],
        '%billing_last_name%'  => $_REQUEST['billing_last_name'],
        '%comment%'            => $notes[0]->comment_content,
    );
    $message        = str_replace( array_keys( $template_vars ), array_values( $template_vars ), $this->options['wc_notify_customer_payment_successful_message'] );
    $this->sms->msg = $message;
    $this->sms->SendSMS();
}