If I had to guess (and I'm not a pro), I'd guess it was a Moen. they can be a bear to pull out. I couldn't tell for sure, but did you have and remove a U-shaped clip first? It's what technically holds the cartridge in. The brass ones are particularly hard to get out after they get gunked up with mineral deposits - you literally have to shear the ring of minerals off the shell since there's so little clearance to get it out. Some people, if they have the time, spritz some strong vinegar on it, which after time will disolve the mineral deposits. Maybe some CLR. Search on stuck Moen cartridges...there's lots of threads that discuss methods to get it out.
If you need to turn the main back on, you might want to call a plumber. There are tools that are supposed to help to pull it out. Some are a joke. And, if you use the tool and it breaks off inside, it is even worse to remove things.