Here's the thing...If you can get away with it great no biggiieeee....
However if AT&T catches on and there is a way to track then they might back charge you the amount...This can happen even 1 1/2 years into the contract.
Just be aware of that.....
you're absolutely right and I've seen it done. when i worked for at&t (a year ago now), there used to be a $19.99 unlimited data plan for "smartphones". well at&t classified one specific phone as a smartphone and it wasn't a palm, blackberry, or blackjack. it was some ***** windows phone w/ a number pad and no keyboard. (click here to see it.)
anyways, a lot of sales guys used to attach this cheaper $19.99 plan to phones like the blackjack and the palm treo 650/750... they mostly did it for friends and family. and it worked... the customers got unlimited data for only $20 (at the time unlimited data for a blackjack or treo was $40).
well guess what happened? at&t/cingular caught on and back charged every single customer the difference. some people owed as much as $500-600 because they had multiple lines (family talk). no one was fired because at&t wasn't too specific on their definition of "smartphone" or the attach policy, but they did make everyone pay up.
So ya'll beware. AT&T isn't completely stupid and they may very well figure out the scam. And when they do they'll most likely make you pay up.
Question - when you first purchased the phone, didn't you have to sign a contract with ATT? Did you not choose your plan at that time? Why weren't you required to activate the phone in-store? I'm surprised they allowed you to take it home.
To others:
What if you took your first-gen iPhone SIM and put it into a 3G BlackBerry? Is that "stealing"? What if your friend decides he doesn't want his 3G iPhone anymore and gives it to you, so you use it with your first-gen iPhone SIM - is that "stealing" as well?
fyi at&t isn't selling a 3G blackberry (yet). and if you know the difference in price plans between phones, yes, it's considered stealing; everyone knows that $19.99 data plan was for the 1st gen. iphone only. some may be able to legitimately claim ignorance, but i'm betting no one here can.