protected function isNationalNumberSuffixOfTheOther(PhoneNumber $firstNumber, PhoneNumber $secondNumber)
    {
        $firstNumberNationalNumber = trim((string)$firstNumber->getNationalNumber());
        $secondNumberNationalNumber = trim((string)$secondNumber->getNationalNumber());
        return $this->stringEndsWithString($firstNumberNationalNumber, $secondNumberNationalNumber) ||
        $this->stringEndsWithString($secondNumberNationalNumber, $firstNumberNationalNumber);
    }