How to not use data on Iphone 4?

I just got of deal on Iphone 4 but did not get any monthly data. Therefore any time I use data I have to pay huge amounts.

So how can I disconnect it so I can only use Wi-Fi when it's available like on campus and still make calls and everything?

I know little about it and would appreciate any insight.

Go to settings-->General--> Cellular--> then change the on/off switch for Cellular Data

This will restrict all data to only Wi-Fi Use.

Make sure you have Wi-Fi turned on. Also under setting general network make sure you have 3G off and cellular data off. Your phone will work like normal without using your data.

Settings > General > Cellular > Cellular Data off

It's pretty simple, really.
1. Go to settings.
2. Click on the "General" Catergory
2. Click on the "Network" Subdivision
3. You will see a bar that says "Cellular Data." it will either be switched on or off. Make sure it is off. If it is, it will stay like that, unless if you manually change it using this same method. If you do get cellular data sometime in the future, turn this feature back on, but remember to switch it off when you're not using the data so you can fully utilize the data and it will not run out too soon.
Hope this helped and have fun with your new iPhone!

Turn off cellular in settings… Very simple.