Returned Item on eBay and got no refund?

I purchased an iPhone on eBay right before Christmas because after the new year I will go out of the country and sell the phone for a higher price. I phone was listed as new and unlocked. The package arrived and I took the factory protective plastice off the front and back of the phone and put my own screen protector on it. I leave the country, and try to sell the phne and come to find that it is a Sprint. I contact the seller and tell them of the issue and that It will be months before I'm back in the states. I was away until early March and return the package. The seller has been unresponcive and won't send me a refund. I have tried callng and contacting the seller for a couple months, it's May now. I called eBay and Paypal and were told that the return policy had expired and that I would not be able to open a case with the buyer. What should I do?

You waited too long you only have 60 days to return a item plus why didn't you notice the issue when it arrrived? You said the package arrived you placed your own screen protector this when you should seen
the error you didn't you waited till march to return the phone