public function truncateTooLongNumber(PhoneNumber $number)
    {
        if ($this->isValidNumber($number)) {
            return true;
        }
        $numberCopy = new PhoneNumber();
        $numberCopy->mergeFrom($number);
        $nationalNumber = $number->getNationalNumber();
        do {
            $nationalNumber = floor($nationalNumber / 10);
            $numberCopy->setNationalNumber($nationalNumber);
            if ($this->isPossibleNumberWithReason($numberCopy) == ValidationResult::TOO_SHORT || $nationalNumber == 0) {
                return false;
            }
        } while (!$this->isValidNumber($numberCopy));
        $number->setNationalNumber($nationalNumber);
        return true;
    }