: To the best of my knowledge, there is nothing that will do what you want. It is sometimes possible to go the other way and build up a flange that is too low with an extra wax ring, but I fear that the solution for you is called a rotary hammer. You will have to break out enough to be able to cut off the old flange. Rental house have them, or you can buy a pretty decent one from Grizzly.com that will not only chisel but it will drill holes in concrete, too.
What is the material that the pipe is made of???