Actually, I'm the one who is giving w/o and canceling the matches.
Our rules are really simple, We've got logs in our communicator where we can see who was online and when, ofk what is he writing in EACH! challange and those are arguments for me, what to do with any match. As you saw for sure, I'm always writing the reason, why my decision was made like that, so I'm pretty sure that actually system of taking care the challenges is in a fair play spirit.
All of you can fell free to pm me here and ask me or show me some s/s why you should win match vs xx player and every other thinks which are related with this case.