If you receive something other than exactly what you ordered, the correct type of case to file is a "not as described" case. Then you return whatever you did receive for a refund.
If you ordered more than one, and received only one, start return cases for the entire order and return what you received.
https://www.ebay.com/help/buying/returns-items-not-received-refunds-buyers/return-item-refund?id=404...
If the seller does not pay for return shipping (overseas sellers may not be able to provide prepaid shipping labels through eBay) or cooperate, after three business days you should be able to ask eBay to step in and refund you.
If you receive nothing at all, but tracking shows delivery, see here for how to handle that:
https://community.ebay.com/t5/Buying/I-tried-contacting-seller-i-tried-contacting-fedex-i-tried/m-p/...
If you waited too long for help from eBay, you may still have some recourse through your payment method. PayPal and many credit cards offer up to six months protection in some cases.
What kind of feedback does your seller have? Look closely at the comments, particularly any negative ones.
You can avoid many issues by choosing to only do business with experienced sellers that have a proven track record of delivering similar items as seen by examining the seller's feedback page, and by avoiding inexperienced sellers, sellers with patterns of negative feedback indicating serious problems, or sellers with large gaps in the selling history or recent drastic changes of seller behavior.
