One of two things are going on here. 1) The battery has gone bad and it needs a replacement 2) The phone has experienced a *glitch* and needs to go through the hard reset process. I didn't see you're phone model listed so try doing a net search for the reset process before getting a new battery. Worse case scenario is that you have other hardware damage on the upside when you go to get your battery replaced they will do a diagnostic to assure that's the issue.

Sorry this is late in coming but to fix the frozen screen try using your finger nail to get under the side of the screen and lift up.... note... keep your nail under the screen as you run around the edges as it does pull out stuff like pocket lint that gets stuck in the craves.... do this all the way around the screen to the best of your ability... it worked for my sgh-a877... but I didn't really try to lift up on the screen until after I did the code reset, was stuck with the touch screen calibration, lost everything and decided I wouldn't mind any side effects if I lifted the screen to far and popped it off.....(the screen never popped off) phone is fully functional again