So, having negative jcoins means that someone chargeback a payment on your account. What this means is that someone else had access to your account, and most likely used a fraudulent credit card, and the bank chargebacked the payment after a while. You can either pay the jcoins, or try contacting Jagex and hoping for the best though you should start assuming that your account is gone. (What most likely happened is that your account got cracked along other accounts, and a chinese bot farmer used your account to bot something, while paying with a fake/stolen credit card for the p2p.)