Trying to remove seatpost, twisting seat just spins clamp not post – suggestions?

that seatpost above is also just a clampy, so the thing with the least amount of friction will spin. Either 1) Tighten that clamping seatpost that is spinning more or 2) get a proper monkey wrench, like one would use in plumbing, attach, tighten. As long as you spin in one direction, the monkey wrench teeth will bite into that seatpost and assuming it’s not galvanically corroded down the inside of the bike frame (*fingers crossed*) it’ll be spin.

If your seatpost is actually stuck, you may have to resort to seeking help from a shop familiar with stuck seatposts. There are all sorts of methods, involving brute force, chemicals, torches, etc. Basically determine how much do you really like that seatpost and how badly do you want it out of that frame.

Remove saddle. Lift bike and place post in bench vise. Twist whole bike. Works better with two persons.

A lot of patience, you added croil, which is good. I’d suggest adding some croil every hour or so over a day. Then leave it sit for the night. Try clamping the seat on good and try moving the post. If it won’t budge pour a few pots of boiling water over the seat tube, this expands the frame and hopefully frees the seatpost.

If this won’t work you can check youtube for seatpost puller constructions, maybe build one of those yourself or check if a bikeshop has something simmilar.

Here end the non-destructive methods, now i’d suggest clamping the seatpost in a vice and using the frame to wrench it loose.

Your last resort is to saw the seatpost out of the frame using a metal saw, hopefully it won’t get to this point.

Keep adding oil and wacking with a rubber mallet where the seatpost is inside the frame. Put a piece of tape so that you can see progress. Step on chainstay while rotating seat and pull upwards – works better with 2-3 people to help hold bike so that the puller can just pull and doesn’t need to worry about stabilizing bike. Then you can put a foot on the chainstay and the other on the downtube – this allows you to get better upwards pulling. You should be able to get enough of your foot onto the downtube without pulling the crank on the L side of the bike.. You can get it out. The seatpost is rotating. If that doesn’t work out the seatpost in a vice, spin bike and pull – works better with 2 people. An extra pair of hands or two helps. There are seatpost pullers in existence but it doesn’t look like this bike needs one – just extra muscle.