ok so i just bought my iphone4 about 4 days ago and it works like a charm. until i noticed that whenever i get a message even when it's on the lock screen, the screen doesnt turn off until i unlock the phone. i figured that this is a problem since sometimes i leave my phone for a long time then when i come back to it, the screen is on and 30% of my battery is drained. the screen does dim and does auto lock from the springboard so that's not a problem. any suggestions?