Can i set my iphone so that it only uses Wi-Fi?

I didn't realise but i was out of range of my Wi-Fi and i used 200 bucks worth of credit on data, so is there a way that i can make sure my iphone doesn't access the internet or download from itunes unless its on the Wi-Fi network at home?

Yes you can… On your home screen go to "Settings" then scroll down and tap on "General" and then select "Network". Once you are there switch "Cellular Data" to "Off".

It is not necessary to change "Enable 3G" as following the steps above already takes care of this.