Don't do it. Find another way to mediate it on your own. The buyer took the items off of the account I sold then claimed I recovered the account in order to get his refund. Despite sending loads of evidence to Playerauctions to show that I had transferred the account and ingame mails to show that he had done in-game activities even after he claimed he had no account access, I had to wait a week per reply from Playerauctions to simply have them pester me to let them conclude the deal in his favor.
Not only didn't get the payment, but spent almost a month maintaining an account that by all rights and promises by Playerauctions should be the buyer's, and I ended up losing money due to the buyer using up items, such as my APEX.
The Live Chat CS reps are nice and respond quickly. Any email systems are dreadful, and if there's any problems with your order, that's what it turns into. They ended up contacting me from two different email addresses as well as an online ticketing system. I answered the first one, they would message me from the second saying I had not answered them. I answered the second, they did the same from the third.