Apologies for the inconvenience, I think I transferred my Frostmourne account onto the icecrown server by mistake without recovery just a couple minutes ago. I haven't played WoW enough to know better. Would be really glad if something could be done
It's pretty much virtually impossible to do a character transfers and all the steps involved in it by mistake.
Character transfers are one of the various services noted as irreversible, which means we won't undo it after it's done.
Even if the above weren't true, Frostmourne's season is over. Your only option besides transferring the characters to Icecrown is abandoning them until they are eventually deleted, which you can emulate by deleting them right now if you like.