If the suggested tricks to remove the sump plug did not work, I advise caution about using heat and a blow torch. A much worse problem could well arise.
This is my suggestion (which normally does work even for really bad plugs):
engine hot; raise the car as high as possible on axle stands; with a hacksaw carefully cut a relatively deep notch in the rim of the plug; use a very good small chisel and light hammer to undo the plug by tapping it through the notch. Care and patience are necessary. Obviously a new plug will be needed after all this. When fitting a plug, make sure it has a good quality copper washer and do not overtighten the plug.... This avoids this sort of problem.
All the best
Andrea