Your credit rating is not determined by how many times you get ripped off by scrupulous merchants.
Hmm, these particular ones strike me as more unscrupulous than anything. =]
Also how can I chargeback a paypal transaction? Its been a week since I paid and there's no response from seller.
Contact PayPal. They have strict measures against bad sellers (mostly in conjunction with eBay, but I'm sure they'd listen regardless).