Paypal — Negative account balance

Website:

Paypal.com

Apparently paypal just refunds buyers on your expense without even it being legitimate.
PayPal has wrongfully charged me for a refund saying that the item was not shipped when in fact I have concrete evidence of delivering the item in question.
The customer care does not help and just keeps on rejecting my appeal.
The buyer has scammed me this is called buyers scam on PayPal where they recieve the item and then request for a refund and PayPal imitates it at your expense.
Paypal is helping this scammer get away and worse punishing the innocent. Please help.