iphone4s internet not working

iphone 4s internet not working. my phone have singnal while using. on the left top corner have the display of "4G" and i can text or phone to someone.

but i can't use my internet. it is all fine since this morning. when i tried a web page, it goes slower than before. after 1 hour, the internet totaly can't be used.

my wifi part couldn't be used either. but it began at december 2012. and i don't usually use the wifi. so i didn't pay attention to it. wifi part is sometime good sometime bad. mostly after i restar it, the wifi can be used for 1 or 2 muniutes.

i was not sure whether or not is the problem of att. but other members of my family plan are all fine at internet.

which part of phone would be the problem? especially for the hard ware parts. i think there would be some problems in hardware. i always drop my phone unintentionally.