Empty Collection :: CollectionFactory Approach and getCollection approach both give empty result

Try Below code,

public function fetchRate()
{
    $var =2600;
    $postcode_rate_row = $this->stRatesCollectionFactory->create()->getItemsByColumnValue('postcode', 2600);
    $collection = $this->stRatesFactory->create()->getCollection();
    $collection->addFieldToSelect('*')->addFieldToFilter('postcode',array('eq'=>2600));

    $this->logger->debug('Rate Collection:' . var_dump($collection->getData());

    foreach ($collection as $rate){
        $this->logger->debug('Rate is:');
        $this->logger->debug(var_dump($rate->getData()));        
    }

    $this->logger->debug('Rates are: '.var_dump($postcode_rate_row->getData()));
    return $postcode_rate_row;
}