I recently called AT&T support for help setting up my new iPhone 3G.
The AT&T menu system wouldn't recognize numbers entered via my iPhone dialer.
Initially the menu recited my mobile number and asked me to press 1 to verify it was correct. I pressed one and was then asked to enter my mobile number. After entering my mobile number I was asked to enter it again in an endless loop.
Even worse is that if you do not enter anything, you are not eventually connected to a live operator or default extension, instead you are disconnected.  This is sooooo wrong! If the menu system can't register the keypresses, or a user doesn't enter anything send the user to a live person. Verizon does this right.

So, I had to call AT&T support from another phone even though their website recommends that I call from my mobile phone.
I was calling with a very simple question. "What is my AT&T wireless email & sms account address".  This information should be on their website. I logged into my AT&T wireless account on-line and searched the website, my account and support forums before calling.

Having this info somewhere on-line would have saved them the embarrassment of not having a pbx menu system that works with the iPhone. I have already encountered several menus that do not work with the iPhone. If apple sold PBX systems, then that would explain that.

After finally talking to a support person I was told my sms address was my-10-digit-mobile_number@sms.att.com
That didn't work so I was told to try txt.att.com. That didn't work either so I was told to try mms.att.com which didn't work either.
I was then told that the txt server was down and that I might not receive any messages till it is fixed. In the meantime I received bounce backs from all my previous test stating host not found. After some more digging on-line, I found several references to txt.att.net so I tried that and this time got an unknown recipient message back from the server. Progress! I then tried my 9 digit number instead of the 10 digit number the support person told me to use and bingo. Now I can have my server send sms messages to my phone as well as give out my sms address to friends and family.

So to recap, not only was it impossible to call support on my new IPhone, but the information I received was wrong in several ways. Had I been a normal non-technical user I would not have been able to figure this out. In my experience iPhone / apple users are the least technical users there are. Otherwise they would be running Linux or BSD. Apple users just want something that is simple and works and a physical store to take their hardware to when it breaks. I know this is a huge generalization, but ease of use is one of the major selling points of Apple products. That being the case I had expected AT&T's iPhone support to be excellent, but the person I spoke to told me that AT&T doesn't support the iPhone and from the mis-information I was given they do not appear to support their own products either.

Hey Apple, do you really want to lock yourself to one carrier?
This seems like the wrong move. Didn't you learn anything when you decided to make your own proprietary hardware and lock your software to it? PCs kicked your ass and own 95% market share because PEOPLE WANT CHOICE.