Can I put an At&t samsung impression sim card into iphone 3g?

[Olivia]

Will it work if I already have a data plan? Or do I have to buy a specific data plan for the iphone?

 

[Unregistered]

You can use the At&t sim card in iphone 3g if it not locked with any other network provider ..If it locked means make it unlocked by getting the remote unlocking service from an online vendor like Unlocking4u.com.