public function addPhoneNumber($phoneNumber)
    {
        Piwik::checkUserIsNotAnonymous();

        $phoneNumber = self::sanitizePhoneNumber($phoneNumber);

        $verificationCode = "";
        for ($i = 0; $i < self::VERIFICATION_CODE_LENGTH; $i++) {
            $verificationCode .= mt_rand(0, 9);
        }

        $smsText = Piwik::translate(
            'MobileMessaging_VerificationText',
            array(
                 $verificationCode,
                 Piwik::translate('General_Settings'),
                 Piwik::translate('MobileMessaging_SettingsMenu')
            )
        );

        $this->sendSMS($smsText, $phoneNumber, self::SMS_FROM);

        $phoneNumbers = $this->retrievePhoneNumbers();
        $phoneNumbers[$phoneNumber] = $verificationCode;
        $this->savePhoneNumbers($phoneNumbers);

        $this->increaseCount(MobileMessaging::PHONE_NUMBER_VALIDATION_REQUEST_COUNT_OPTION, $phoneNumber);

        return true;
    }