There are a lot of different things I see stated on ways to get around AT&T automatic application of expensive data-plans when they detect that you're using a smartphone. Some people have said that all you have to do is turn off 3G Data Use from the menu of the new phone BEFORE inserting a new SIM card, and then insert the old dumphone sim card and everything will work. Some people make vague allusions to changing the IMIE--to which some people claim that's illegal, and others claim AT&T or random clerks at Radio Shack will do this for you upon request. Still others claim that all you need to do is install a "data blocker" program onto the smartphone before switching SIM cards, and it will do the trick.
The basic goal seems to be "hiding" the IMEI number from AT&T.
So, my question: how does AT&T recognize the IMEI number? Will they see it only if the phone is active on their 3G/4G/LTE networks? Or do they see it "through" the normal dumbphone calling networks?
My apologies if this is a stupid question. I really don't know anything about phones are anything about non-PC electronics or software in general. Basically, I'd like a smartphone but refuse to pay an exhorbitant monthly fee for a feature I'd never use (wifi is everywhere I go), and am not in a position where I can switch carriers, and it's like I'm part of a(n evidently sizable) demographic that no one wants to market to.