Sounds like normal behavior to me.
When you put the phone up to your ear, the light sensor turns the screen off to save on the battery and help keep you from touching the screen and pressing something you didn't mean to.
Take the phone away for a second or so and the screen comes back on (or should).
Samsung Galaxy Express SGH-I437P 4G LTE ---soon to be--- on Aio $40/35 Basic Unlimited T/T+500MB H/S Data Plan
"If it ain't broke, fiddle with it until you break it, then fiddle with it until you get it fixed"