How do I keep from activating facetime while on a call When making a call my cheek hits the screen and turns on facetime etc. 

How do I stop this?
Modern touchscreen phones have a proximity sensor, that emits IR light and measures the bounce back from nearby objects (if any). It's meant to detect your phone's proximity to your face. Perhaps you have a malfunctioning proximity sensor that's never detecting your face.

Does your screen go black when you cover the top (from the top of the display and up) with a finger?