public function aroundGetNotLoggedInGroup(
        \Magento\Customer\Model\GroupManagement $subject,
        \Closure $proceed
    )
    {
        /* call parent to process other around-plugins */
        $result = $proceed();
        /* check referral code in registry */
        $code = $this->hlpReferral->getReferralCode();
        if ($code) {
            /* and return referral group if code exists */
            $groupId = $this->hlpConfig->getReferralsGroupReferrals();
            $result = $this->daoCustGroup->getById($groupId);
        }
        return $result;
    }