How do I appeal a charge back?

[Txbraveheart]

I sold jewelry on Craigslist and agreed to use Paypal as the payment provider. The money arrived in advanced which I transfered to my bank account.  I shipped the product via USPS (using tracking and insurance) to the address supplied. Four days later the transaction was disputed for a reason that was never made clear. I then provided the information to PayPal (including tracking) assuming it would be ok. Two days after that, the buyer informs me the package had arrived and thanks me. USPS also sent me confirmation of delivery.        Today, Paypal reversed the transaction and left me with a negative balance despite all of the information above. 

How can this be fair and how do I eascalate this decision?

[kernowlass]

@Txbraveheart

Before appealing it why not just contact the buyer and state that due to the fact the payment was disputed and that was not cancelled the funds have been returned to him and send him a money request to pay again.

If he does not then give c.s. a call.

[Txbraveheart]

The buyer is not responding to calls or emails.