I hear you, Fanime is being absurd with this stuff. Anyways, you'll have to contact your credit card company to initiate a chargeback. When you do, be clear that you contacted Fanime twice, and got no response, and that you are seeking a refund because they changed their policy for attendance after you already paid(no need for details here unless they ask). Basically that means you agreed to the terms, paid, then they changed the terms afterwards. The credit card companies really only care to see that you did what you could within reason, and could not settle the matter due to the other party(Fanime) not cooperating. That should be enough to get the credit card company to back you and get your refund. This no guarantee, but it's the only recourse we've got.