Should I turn on or turn off my cellular data on my Iphone 4?

I want to use as little data from my monthly plan as possible. Should I turn off my cellular data? It says it would restrict all data to WI-FI if turned off.

Turn off 3g.
cellular data is used for calls and texts.

Yes, if you want to restrict your phone from using your data then turn it off. It will force the phone to use Wi-Fi and will not cost you any precious data. That being said it really depends on what your data plan is and how much you use the phone. For instance if you have a 5gig data plan and you are not constantly watching youtube video's or movies then I would say it would be hard for you to use all that data. You can turn your data on AND turn on your Wi-Fi and it will automatically connect to Wi-Fi when you are within range as an alternative. If you are really worried then turn the data off.