So I put up a bag on ebay in a fixed auction. This guy sent a best offer that's pretty close to the BIN price, so I end it early to sell to him for $800 ($780 plus $20 for S&H). I sent him an invoice, and he responded by saying that he wanted to pay it, but for some reason that we can't figure out, he can't complete payment w/o sending $30 for S&H, instead of $20 (which is what I charged him). So the ebay invoice asked for $810 total. I sent him another invoice with PayPal, asking for $20 for S&H (for $800 total), and I told him to disregard the first invoice. Then I got an email from PayPal, stating that an unauthorized transaction for $810 was made, and there's a hold on these funds. The guy sent me an email 5 min. later, stating that he accidentally paid 2x, the first time paying $810, the other time paying $800. He really did, so I have the $800 minus fees in my PayPal account, and they're asking me to resolve the issue. The buyer is desperately pleading with me to refund the $810 because of tight funds. I've never had this happen to me before, so I just want to know if anything bad will happen to me because of this "unauthorized" claim, and does the buyer sound suspicious? He has 82 feedback, all positive except for 1 negative, and he's been an ebayer since 1998.