you need to do a little testing on your own to see where the problem lies.
....remove the battery, wait, put it back in...try turning it on.
....did you hold the power button long enough.
....was there a power surge, or other electrical problem
....was the phone dropped or damaged
....are you sure it charged, maybe the charger broke and its depleted
...so many things it could be...not counting any strange issues or hardware failure.