I am having issues with my new iPhone 4, with iOS 4.2.1

During a call the phone does not disable the display and keypad like the iPhone 3G that I had.

I am frequently hangingup on people, having buttons pressed and other aggrivating issues.

I checked during a call today and while the phone was near my ear and I was talking, the display never went off and I accidentally pressed buttons on the keypad by having the phone near my face.

Is there any way to correct this?