Leave them a 1 star review. Then send an email to every address you can find for them. Point them to this thread. promise to leave a followup posting letting people know if your withdrawal is processed or not. Report back here and tell everyone if they respond or not and if your money arrives or not.
BTW - Close all open positions in your account. If they have some sort of inactivity fee, may one tiny trade every 3 or 4 weeks.