Keep the phone unlocked when on a call

How do I keep the phone unlocked when I am talking to someone on the phone. When I want to hangup the phone I have to unlock the phone to hang up. How do I dissable this. When I want to hangup I want to hang up. Not unlock the phone and then dissconnect the call. Thanks

when the phone is locked and you recieve a phone call or are on the phone the hard keys send and end should still work, the one thing i hate is the volume is locked.