Can you turn data off on an iPhone?

I'm looking to get an iPhone. I understand that you have to pay a monthly charge for data no matter what, but to be quite honest I do not go many places that don't have Wi-Fi, nor do I feel I need to be able to get on to the internet everywhere I go, so I was hoping there's a setting to turn off data so I can get the smallest plan possible.

Is that an option?

Added (1). I'm not saying not GET a data plan, but is there a way to turn it off and only use wi-fi? Why is it "necessary"?

No its neccesary

I leave my Wi-Fi turned on so that all data comes through it rather than coming to the phone itself, which could run up the phone bill quickly. I think the only way you can fix your data so it doesn't go directly to phone is to do so through your phone provider as I did with my previous phone. Ask if they can turn it off. I don't think they can with these phones.
With the phone I have now, I have to have a data plan whether I want it or not because it has the capability to get Internet, movies and games. The only way to avoid data charges is to get one of the regular phones which doesn't connect to the Internet.
Yes, at home, I use Wi-Fi only so it doesn't run up my data usage when I want to watch youtube or other videos. Just go to settings and leave it connected to Wi-Fi.