What happens when I turn the 3G off on my iPhone 4?

I have to pay for Internet, but if I turn off the 3G and use the Edge Internet, will it make the Internet free? Am I paying for the entire Internet or just the 3G?

You only pay if you use too much 3g, for example if you buy 2 gbs per month and use over that, it charges you on top of the 2 gbs! But if you use less that the 2 gbs, you still pay for the whole 2gbs! Unless you have an unlimited plan, then you can use all you want!