Hmmm looking at their site now I don't easily see a button to file a complaint like they used to have. So yeah i'd nose through the forums and maybe ask there. Before they were active in trying to kind of act as a friendly mediator and I found them very helpful and they helped me get some positive results a few times where the books were clearly in the wrong. If they aren't doing that any more it would be a bummer.
Doing a quick search online I found this site/link too...i have not tried osga.com before. Good luck!
www.osga.com/.../Complaint_form2017.htm