solution to this problem
I can't take credit for this fix, but it works! I had this same freezing-while-swapping-camera-angles problem.
"First go to settings. Then go to Phone. Where it says FaceTime tap it so it turns off, then retap it to turn it back on. Then press the button on the bottom of the iphone to go back to the home screen. Next, Press that same button along with the top power button until you see the silver apple. Only let go when you see the apple, because there is an option to turn off the iphone by sliding the bar, so just hold the two buttons. The iphone will basically hard reboot. Dont worry you wont lose anything. Then it will start up by itself. Next, make a call and try it. It will be fixed. Hope this helps everyone!"