Toilets, Sinks, Showers, Tubs and Disposals - Toilet water supply valve leaking

HELP! I need to install a new supply valve line from wall pipe to toilet cause the old one broke. I could not get off the old nut and swedge thing so I just installed the new valve with that old nut and swedge. Now it leaks. How do I get this old nut and swedge thing off the copper pipe coming out of the wall?? I put teflon tape on threads too and still leaked.

Ok, I got the leak stopped by backing off nut, and retightening. Hopefully it wont leak again. After some reading, there is no way to remove a compression nut and sleeve. You would have to cut it off.

That is correct. When a compression nut is tightened, it presses the ferrule into the copper pipe. Even if you cut the ferrule off, there would be a depression that would probably leak. One trick I have learned for leaking compression fittings is to take a piece of heavy string, pull it across a candle a number of times to coat with wax and then wrap two wraps of this string between the nut and ferrule. Tighten down the nut and MANY times this will stop the leak.