I know you're frustration, but this is the correct way to make a complaint.

It's better for you to attach the whole proof where you're already give full KYC to them and the reason why your account got blocked, there's must be a reason behind that since he doesn't easily accuse a player without any proof.

As the amount is only $400 it's make me not believe Fortunejack is a scammer, just do what I said above.