public function phone_number_old_and_new($my_number = '', $my_format = NULL)
    {
        if (empty($my_number)) {
            return NULL;
        }
        try {
            $old_number = $this->phone_number_convert($my_number, 'old', $my_format);
            $new_number = $this->phone_number_convert($my_number, 'new', $my_format);
            if ($old_number != $new_number) {
                // Nếu sau khi so sánh convert số cũ và số mới khác nhau -> trả về 1 array
                $result = [
                    $old_number,
                    $new_number
                ];
                $this->_debug->info(__FUNCTION__, 'Result: ' . $result);

                return $result;
            } else {
                // Nếu không khác, trả về string
                $result = $this->format($my_number, $my_format);
                $this->_debug->info(__FUNCTION__, 'Result: ' . $result);

                return $result;
            }
        }
        catch (\Exception $e) {
            $message = 'Error File: ' . $e->getFile() . ' - Line: ' . $e->getLine() . ' - Code: ' . $e->getCode() . ' - Message: ' . $e->getMessage();
            $this->_debug->error(__FUNCTION__, $message);

            return $my_number;
        }
    }