I've got to say that so far, I'm disgusted with the lack of knowledge AT&T have displayed with the iPhone. It's almost as though they've been caught on their backfoot and are totally unprepared for what the iPhone can do and will need in the way of support. Some examples for you:
I'm a UK national who was on extended vacation to the US. I had to have the iPhone as soon as it was released. Because I didn't have a US Social Security number I couldn't get a 'normal' contract and had to go prepay, which is understandable.
As soon as the phone was activated I started getting flash messages informing me "your last transaction cost $0.00". These messages came in at all times of the day and night, even when the phone wasn't being used. Often I would have to clear a LOT of these messages before I could use any features of the phone. After speaking with AT&T regarding this, the best answer they could give me was "switch your phone into Airplane mode, you won't get the messages". Yes, this is true, but it also would interfere with my incoming calls... The AT&T agent informed me this was NOT the case and that I would still get my calls. Hmmm... right. I called back 3 times and was given exactly the same advice.
(The messages stopped themselves after a couple of months. Which was nice).
Recently I started having problems with data access. I called Apple who ran all sorts of tests, took the phone into the local Apple store and had the hardware checked - no problems. So, getting onto AT&T was the next step. 5 calls were made on the first day and in every one of those calls AT&T insisted that it was an Apple fault, not them. On two calls my protests and explanations were ignored and I was cut off mid-sentence to be put through to Apple Support. Not happy.
Eventually, an Apple supervisor came in on a call with the AT&T supervisor and demanded he put it right (at this point, I've had no data access on my phone unless I'm in a WiFi spot for 6 days), long story short - the AT&T rep disconnected my data plan without noticing that it couldn't be reinstated for one month and I'd be charged for data until then... When I pointed this out to him he put the Apple rep & I on hold for 40 minutes before coming back and telling me data charges would be refunded by AT&T until my data access plan was reinstated. Not ideal, but ok.
Sadly, this didn't fix my data access problem. In 2 weeks I've had access to the Edge network 3 times. The first session used the initial $20 credit (for less than 10 minutes of access to email through Safari), my second session cost $21 which was refunded with no questions by the one truly excellent AT&T staff member I've come across (Thanks Stephanie!) who read my account notes and saw the full history.
My third session was this last Monday, I was on the phone for 36 minutes explaining the situation to an obtuse young man who insisted my notes mentioned nothing of a refund of data charges (even though the previous agent had found this information straight away). We argued, I was accused of attempting to profit from this issue, I spoke with a supervisor, who informed me AT&T would never have agreed an ongoing refund like that. Getting angry I demanded a full refund of the iPhone purchase price and a refund of 3 months service fees for breach of contract (which is exactly what they informed me I'd have to pay should I terminate my agreement in the first year, yes. Even though I'm on prepay...). Now, at the beginning I was only asking for a refund of a $14 fee for the iPhone doing its' thing and updating weather & stocks etc but in the end I was looking for nearly $1000 (which I was perfectly entitled to request as AT&T are failing to supply the service contractually agreed upon). At this point the Supervisor relented and agreed 'as a gesture of goodwill' the $14 refund. Wow. Thanks.
My iPhone is now sitting on my desk switched off waiting until the 28th to see if the problem is resolved. I can only hope.
In conclusion, I love the iPhone but I can't stand AT&T. If Apple would allow the phone to be unlocked without limiting it's updates I'd be a very happy man. Be wary before signing with AT&T.