Problem with iPhone 3G

[Mahaa93]

Recently, my iPhone 3G has been acting very weird, and I wanted to know if the following reasons are valid for an exchange at ATT.
First off, I noticed that games (i.e Fastlane) run more fluidly on my brother's 1st gen. iPod Touch, whereas on my phone, it tends to lag at some points in the game.
Secondly, when I run safari over 3G with full reception, it simply says "Page failed to load because it is not connected to the internet." After refreshing the page 5-10 times it finally beings to load, but very slowly.
Finally, a crack has surfaced the back of my phone, most likely resulting from heat.

Am I able to make an exchange for a new phone?

EDIT: I'm currently on 2.1 firmware not jailbroken if that helps at all..

[Coral]

If you could demonstrate faulty 3G connection you may have a chance of getting a new one. I guess you would also have to somehow prove that the problems occurred before the crack appeared and that the crack wasn't caused by dropping the phone.
Good Luck.