Did you mark it received with a problem so that PBS knows?  I would PM this person again and state the PBS rules that say the ISBN has to match. The cover  and publishing year does not have to match. But the binding and ISBN does.  Also the book shouldn't have writing in it unless it was a text or cookbook and you were told about the writing before hand.  You can't force them to give a credit back but if you PM them a couple times you might.  PBS won't step in unless they have several complaints against them. Hopefully they'll step up and do the right thing.