well I had tried to do that a couple of other times, but I made the mistake of FIRST telling the ATT person that I had an unlocked phone. We're talking about two long calls to tech support and one IN PERSON visit to a devices "support" center. When you tell ATT that you have an unlocked phone, they close their ears and don't care. You are not their problem, which makes sense because they have problems all day long and one less would be welcome.
But it turned out, after I finally, today, after reading that post again, decided to LIE to the tech support person and she actually LOOKED at my account, that some bozo from ATT had TURNED OFF MY DATA PLAN COMPLETELY. I had originally had an unlimited plan, but now I had nothing... pay per use that didn't even work.
So moral of the story is to go ahead and try to cut the SIM if you need to, or just go ahead and lie to ATT because they do not have your actual interest in mind if you are not on one of their branded phones.
So thank you for the response, you caused me to re-read the article and gather the courage to fabricate a story that eventually made my phone work.