If i cut up my sim card, that is 3g compatible and has imei number for like a sony ericson bar phone, into a micro sim card and use it for an iphone and sign up for like a $10 unlimited data plan for att non-smartphones, will that work?
I can't answer the technical portion of the question, but I have a feeling that carriers have policies and defenses in place for this type of circumvention. I doubt you'll get away with it.
If i cut up my sim card, that is 3g compatible and has imei number for like a sony ericson bar phone, into a micro sim card and use it for an iphone and sign up for like a $10 unlimited data plan for att non-smartphones, will that work?
No, that wouldn't work. AT&T knows what kind of phone you are putting your SIM card into, and once they detect the iPhone, they'll make you add a $15 or $25 plan.
At least in Canada, the "non-smartphone" data plans (don't exist anymore) are only for WAP browsing, so any normal smartphone that uses HTML will not be able to use it, so you would have to change it to a normal data plan.
From what I've read about AT&T, they do random checks for what IMEI is actually active rather than the one that's scanned in the system, and if the plan doesn't match the device, they will change it.