Start by contacting the seller. Explain there was a packing error (were they all ordered at the same time?) and that these have not arrived.
Do NOT NOT NOT allow him to offer a replacement. It will never arrive. This is particularly true if the seller is in China. (Long story, but search these boards for 'replacement').
He should send your money back immediately. There is NO reason for any delay.
If you don't get your refund within 24 hours, open an Item Not Received Dispute in the Resolution Centre at the bottom of this page.
If he cannot prove that you already have the rings, he must either refund you or Paypal will and go after him for their money.
This is not a matter of being impolite or pushy. This is a matter of putting on your big girl panties and standing up for yourself.
And again. No replacement. Immediate refund. Or INR dispute.
If you still trust the seller, you can then re-order the rings.
If.