My fears are eased...
I just got off the phone with premier and here is what they told me about the charge showing up on my account as pending for three days and then disappearing. Matthew told me that this is perfectly normal. He said that what they do is put a "pending" charge through to make sure that the account is active/valid. The charge automatically is dropped from your account unless AT&T tells them to go ahead and put the charge through. Once your order has been assigned a shipping number they will re-charge your account for the original amount.
I think this is what some pay-at-the-pump gas stations do. They will put a pending charge of $XX dollars on your account prior to pumping to make sure account is active/valid and then run you actual charge through once you finish pumping. As an aside, I got screwed on this a couple of times in college...wanted to pump $5 worth of gas and had $6 in my account but the pump was trying to authorize for over $6.