Just escalate the claim and be as detailed as possible.
Btw, you are required to send the package back BEFORE you get the money refunded. That's how paypal works. Either way, though, if you file a claim and win (which you almost definitely will) paypal will assure your money back whether he has it in his account at the time being or not, so you will be protected, you will just have to have tracking and proof of shipment back and all that.
If I were you I would take photos of the phone and the damage BEFORE you send it back to him in that case too. Maybe I'm too cautious with these things, but I have been screwed before. You don't want him able to file a counter claim or whatever it is called saying that YOU damaged the item before sending it back or something. You never know, I honestly feel like paypal doesnt' even read the information that is sent to them with those claims so be careful.
I sold a WORKING g3 powerbook on ebay a month or two ago without a powersupply. I described all the information clearly, about it being old, but working fine when plugged in (the batter was dead...and i was using a powersupply from another computer to install things etc) anyway.. i sold it for like 60 bucks on ebay. The person who got it said it didn't work and I was trying to scam them blah blah blah (because clearly us mastermind scammers love trying to scam someone with 8 year old equipment for 60 bucks....), although it was working, he didn't understand anything about the correct powercord and as such filed a complaint saying it was incorrect.
Paypal, despite me working with him to the best of my ability and all my proof the computer was working to paypal, favored him and he was going to ship the item back. I wish I had taken photos of the computer while i was installing things and the condition it was in immediately prior to leaving me, but I didn't and because of that he won.
However, on the plus side, because he wasn't the brightest crayon in the box, he didn't respond by the deadline to paypal, so the claim was dismissed and I haven't heard a peep from him...
but the point is, no matter what side of a dispute you are on, get as much evidence as you can about the product in question before letting it out of your sight.
Goodluck! File that claim immediately!