Western Digital will not honor the warranty

My warranty claim was rejected because I have bought the HDDs from a third party seller on ebay despite I provided them the proof of purchase. Based on the serial number, both the HDDs have warranty. In the past I never had any issues replacing the drives even without proof of purchase or the origin of purchase. I have also a bunch of drives for replacement as I am worried that they will be rejected based on the similar claim.

We are a small business and try our best to save the money all possible ways. We will be in deep trouble if all our claims are rejected including the one mentioned above. I understand that there are frauds involved and WD tries to minimize it. But we have now become the victims. I hope WD understands our pain. I am really nervous now. I would greatly appreciate any suggestions.