Since one of each multi pair is being reported in the IC trading lounge (on the RPG Centre) as being scammers, chances are you were out of luck even if they weren't banned.
But yes, you are definitely out of luck, for the moment. Typically, one of each multi pair is allowed to return after a month with partial asset loss, so you may be able to take it up with them then.
____________"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
Only fools and children dream of heroes.