Ebay: Should i Have investigate by escalating this dispute to a claim?

I am a seller on EBAY... i sold someone a Blackberry storm. to chile. i shipped international. it has been a little more that a month and he is baeley contacting me saying he only recieved a empty box with just foam and no phone. which is a lie. i have the reciept from the post office. it has the weight of the box. an epty box would have weighed less. im absolutly positive the phone was in the box. i think he is just trying to keep the phone and get his money back. in the dispute i told them everything. all he put was i got a empty box. i put all of my info down. about how much it weighed etc. so if i escalate this to a claim what will happe? how does it work? can i escalate it to a claim... if the case was opend on me? what should i do? paypal is my ONLY income. i would nvr do that to any of my customers. i have 100% positive feedback. and the already freezed $300 !!! from my account which i need asap for bills!!! please help thanks