OK, ALL USERS WHO HAVE THE SAME PROBLEM I HAD, LISTEN CAREFULLY: check it out ------ u drop your iphone (the screen does not even have to crack), it drops. Its kinda like shock. When your iphone goes into shock you have to revive it.
Step 1: Plug your device into a wall or any power source. This will provide enough stamina for it to generate electricity through its system. KEEP IT PLUGGED IN.
Step 2: Hold down the sleep/ wake button (the button that turns your iphone on and off). Then, count for 10 seconds with your finger still on the same button (do it aligator style -- one one thousand two one thousand all the way to 10).
Step 3: Slide a finger across the top of the screen just like you would as if you would turn it off. (you have to be precise when you do it: IN THE EXACT SAME SPOT YOU FEEL WHEN YOU TURN IT OFF).
Step 4: Wait ONE FULL MINUTE with the iphone still charging. Then, hold down the sleep/ wake button. If the white apple shows up, then you have probably fixed it. If not, THEN GO TO YOUR SERVICE PROVIDER AND HAVE THEM FIX IT. Just remember there is always a way to fix it besides being excessively charged for money.