It is a flush or extended choke? I would throw the barrel in the freezer for 6 hours. The barrel and tube are different metals, they will contract at different rates. If it is extended, use a pipe wrench, it flush try the choke wrench. Bonne chance...
Depending on why the choke is still stuck in the barrel it is going to be a pia .
No ifs and or buts.
If it is cross threaded there is very little that can be done to remove it safely ..(saving the threads)
If it is rusted in there, then several answers already mentioned should ahve removed it by now.
Have you tried diesel fuel ??
Soak it in enough to cover the threads...
But, first add some heat to the barrel ...just enough to get it hot and submerge the end into the container of fuel oil.
O?f course do this outside with appropriate ppe and a fire extinguisher at hand ( just in case )
The freezer method is an urban myth in my opinion as it will not get the metals cold enough to cause the contraction and expansion required.
Lock tite registered trade mark ) has a product that one sprays on to the effected materials and freezes the metals to very cold temps.
Before all the nay sayers come out, I have tried to remove a stick choke in two guns in the past three years one a Beretta 686 that was put away wet from the previous season and both tubes where frozen solid from rust ..the freezer method had no affect...the firearm was returned to the owner with a recommendation to take it to a gun smith...
The second is a Browning PBS camo that has been soaking in diesel fuel , atf fluid and heat applied to draw up in the threads ...all that has done is screw the camo up and the choke is still in there.
These are not my guns, but I have been privy to the trials and tribulations of the gun owners who have asked for ideas and assistance from amateurs such as myself.
Rob