code: protected function getUnpaidAccountNumber(CustomerGroupInterface $group, string $origin)
      {
          foreach ($this->accounts as $account) {
              if ($account->getType() !== AccountingTypes::TYPE_UNPAID) {
                  continue;
              }
  
              foreach ($account->getCustomerGroups() as $g) {
                  if ($g->getId() === $group->getId()) {
                      return $account->getNumber();
                  }
              }
          }
  
          // Fallback to 'all' (empty) customer groups
          foreach ($this->accounts as $account) {
              if ($account->getType() !== AccountingTypes::TYPE_UNPAID) {
                  continue;
              }
  
              if (0 < $account->getCustomerGroups()->count()) {
                  continue;
              }
  
              return $account->getNumber();
          }
  
          throw new LogicException(sprintf(
              "No unpaid account number configured for customer group '%s' (%s)",
              $group->getName(),
              $origin
          ));
      }
docs: Returns the unpaid account number for the given customer group.
  
  @param CustomerGroupInterface $group
  @param string                 $origin
  
  @return string