There are several lengthy threads in this forum regarding "every trick in the book" for seatpost removal. Search and read.
I have sawn out a few and it's never a picnic, but have had success, also in the heat of battle I got over amped and ruined a couple good frames, so keep a cool head.
Speaking of heat: if you can get a good heat gun, use it carefully and it might be your magic charm, and not burn off the paint. They are easier to control than a propane torch but still require care!
Good luck!
it's a great feeling when you finally get one out, even if the post is trashed.