Do you use data on an iPhone 4s if you're connected to Wi-Fi?

Do you use data on an iPhone 4s if you're connected to Wi-Fi?

I don't think so but to be sure turn you mobile data off like this---Settings-General-Mobile data then switch to off.
When you have done this connect to Wi-Fi and try the net etc i'm pretty sure this will work though i'm sure in the past i have done this. I think i have even tried out a phone without a SIM card over a Wi-Fi network.

Yes. When the iPhone is locked it switched to your mobiles data as this saves battery life. When your using the phone it'll always be connected to Wi-Fi.

Hope this helps