I had issues with that too when ordering through apple. I canceled my apple order and did it through att with no problem.
I will warn you there is a page that looks like they are changing your data plan if you are grandfathered into unlimited...but it does not change anything, just a system requirement of some sort. I called an ATT rep to make sure I wouldn't lose my unlimited data plan before I continued.
I saw the same thing with Verizon in reguards to the No Text Plan, I called Verizon to verify nothing changed, they said the Text plan is attached to the calling plan, looked everything up, and nothing at all was changed. So I would say you have nothing to worry about.
I just checked on ATT site, and so far it looks correct. But I didn't get my 4S order conf email yet, so I will confirm then too. And when it ships. And in person next week. haha
My experience with VZW (AT&T might be different) is that all the 'account changes' made online when ordering do not go into effect until the phone is activated and can be changed upon activation at the store.
If you have any doubts on what your carrier is telling you electronically, go into a store and have them activate it upon reciept. Save yourself the headache of having to deal with it over the phone after the fact.