This can happen from time to time, and I think most of the time they just end up giving the customers a refund. From my personal experience, its better to just

This can happen from time to time, and I think most of the time they just end up giving the customers a refund. From my personal experience, its better to just ask Paypal to refund the money and ask the customer to re-pay. Its a bit annoying, and you may get some disgruntled custoemrs, but a whole lot easier than going through the pain of asking Paypal for an explanation.