will att gophone sim card work on an unactivated iphone?

Ya sure AT&T sim will work in iphone only if it is unlocked one else if the iphone is locked to some other network provider then it wont accept AT&T sim until you unlock it .You can easily unlock your iphone using sites like Mobile-Unlocker.com here they are rendering remote unlocking service to unlock all model iphone from network lock ..After unlocking the iphone you can freely use it with any GSM sim ...