If i put my At&t sim card in a unlocked iPhone do i still have to pay the extra (iPhone) data?

I have a at%26amp;t sim card -without a data plan but adding one is $15 or something

and i'm going to buy a used iPhone 3G and unlock it after jail breaking itIf i put my At%26amp;t sim card in a unlocked iPhone do i still have to pay the extra (iPhone) data?
Neither jailbreaking nor unlocking does anything to prevent the AT%26amp;T network from detecting that you're using an iPhone and adding the data plan to your account.If i put my At%26amp;t sim card in a unlocked iPhone do i still have to pay the extra (iPhone) data?
The Plan data details and it cost details Please call the AT%26amp;T Service Provider....You can get the Unlock code at reliable cost at here http://www.unlocking4u.com/apple-iphone-鈥?/a> and Unlock it...Mobile from the Network Lock,then You can use the AT%26amp;T Network Sim Card.If i put my At%26amp;t sim card in a unlocked iPhone do i still have to pay the extra (iPhone) data?
If u buy and old cigular sim card you can use an iphone as a gophone with no data plan