Paypal buyer claims unauthorized use to get refund?

[traci]

I had a customer purchase a business marketing package from my website for me to provide his project with 1 month of social networking services. I completed the project as agreed only to find that the very day after I completed a month of work, the man filed a PayPal claim citing that his account was used against his will, thereby placing a $399 hold against funds in my PayPal account.

It is my understanding since the "goods" sold are virtual in nature, rather than tangible, that I am protected as a seller. Does anyone know if this is right?

Also, after reviewing the transaction in my PayPal account, I noticed that he is not a registered PayPal user, so must have just used a card on the PayPal invoice, rather than logging in to PayPal. You don't have to be registered with PayPal to process a payment.

I have responded to the claim via PayPal and uploaded all of the evidence I have from our correspondence and the work completed.

Anyone been through anything similar? How did it turn out? Any advice?

Thank you.