Will AT&T charge me if I put my sim card into an iPhone?

I'm currently using a Pantech Link II right now and my two year plan with AT&T has recently expired. Even it expired I still didn't upgrade yet. I have an unlocked iPhone 3gs and I was wondering if I put my sim card into the iPhone will I get charged for data? My pantech that I have now does not have internet so the data is blocked. If I turn off the data and everything on the iPhone will they still charge me? I know that they know that I'm using a iPhone. I was just going to be using the phone like a regular phone and use Wi-Fi instead of their data.

Nope, they will not charge you.