Iphone 3g stuck on red battery or low battery even it is charged for more than 4 hrs?

At first it was okay and i decided to reset all media music and settings of my iphone, while resetting my iphone's battery depleted and now it is stuck in low bat if it's plugged in the computer or charger but if it is not plugged it turns off any help please.

If its 3G then I assume its 3-4 years old. You may want to have a new battery put in it, or just extend to a new contract and get the iphone 4 free… Then its an upgrade on top of it.