iPhone with out data

Hi, im getting an iphone from a friend whos contract is up and has no need for it. so my question can i switch the sim with my current phones sim? my sim is still with att, and i just unlimited call and text, with no data plan. and can i just switch the interenet to wifi from 3g so i dont get charged extra for interent usage?

Just be careful because your iPhone will still connect over EDGE. If you have email, push notifications, etc. turned on, your iPhone will still charge data while not in a WiFi area. Additionally, while I haven't heard of them using the right, ATT reserves the right to automatically add a Data plan to your phone if they discover you are indeed using an iPhone.