I believe I read that your card will not be charged until the phone actually ships, but I could be wrong. Here's what Gizmodo says: http://gizmodo.com/5562910/where-to-buy-an-iphone-4 They always have (pay for) Apple info first ;-)
I was not billed right away. but Shows its all Ready to go. Called ATT to confirm the next day and they said im All on schedule. but was not billed yet. ..