Once again I am replying to my own query because I found (sorta) my answer after posting here.
I have found indication of our data and messaging features in only one place on the AT&T account management page: the Voice & Data Usage Summary, at the bottom of the page. This hints at us having unlimited but indicates we've used zero of that unlimited which is absolutely false. Is this also an indication that unlimited is really unlimited? That AT&T is not even monitoring our usage?
Of course, reading through the above mentioned page more carefully raises other questions as well. What are the additional purchased minutes? Is this how AT&T is labeling the prorated minutes? If so, why is it exactly 100 minutes? Who purchased those? Certainly not me! And why are those being applied to our calls before our regular 500 minutes?
I don't want to call AT&T yet. I dread doing so. If anyone here has made a similar transition as I and my wife have, I would love to hear your story. Did you find these same inconsistencies between the two systems? Were there problems, later, when the other shoe dropped and bills were sent out?