The fine print for my FAN (not an iPhone, yet) says that the iPhone data plan is not discounted.
Here's the quote from AT&T site, "Your account type qualifies you to the following discounts. Service discounts are applied to the primary line under eligible agreements and exclude certain rate plan types and devices (e.g. iPhone data features and packages).
So, I guess my voice fees will be discounted? I don't know what the "packages" in the quote means.