Need help with members doing chargebacks with paypal.

I would like some suggestions as to how I can stop this from happening. My members are doing charge backs claiming that it was not them.

Since I don't have like a ip address of there's when they signed up, how can I protect my self. Paypal is not on my side with the only back up to tell paypal that they logged on to my site and made a subscription payment.

On top of that I'm afraid to even mention the the site name to paypal since they don't accept adult content.

Any kind of suggestions.