Sure its a frozen caliper?
When I did my rear brakes(the first time) a few years ago, I was terribly dissapointed. I did new calipers, rotors and pads. Thought it would make a huge difference.
It turned out that there was a blockage in my rear flexible brake line(both sides). I would step on the brakes and the calipers stopped the car but they would not recoil. Bleeding went fine because the debris acted as a valve clogging the line where the metal bracket was crimped to the line allowing fluid into the caliper but not back out. The calipers stayed clamped on the rotor and over heated - slowly recoiling over the course of a few minutes. The heat was so intense that the finish on my wheels was damaged, and all my brand new brake parts were destroyed.
I'm lucky my car didn't burn to the ground.
When doing your brakes, especially the rear, get new flex lines.