Removing stuck or seized seatpost?

and it's still firmly stuck in the seat tube, there was no way to move it even an inch with heat, wd40, hammering etc
Any other extreme ways ? i'm considering filing one side down for a few hours but how do i get it out of the tube if there's nothing to clasp ?

dude, the heat will not work. u may try and live with it...there is a massive risk to damage the frame. Try pouring shave ice in the center of the tube... then try to hammer it with elastomer hammer head only...see what happens