iphone 5 brightness not working at all on IOs 6.0.2

i had my iphone 5 for three weeks now and i just noticed that my screen brightness doesnt change at allniether manually and nor automatici tried to calibrate it using the automatic in the dark then revealing it to the light.. tried soft reset and hard reset.. but my brightness wont go down.. its the maximum even when i put the slider to the farest left. .. im hoping its not a hardware defect..please help..