I'm brand new here, as I was finally able got get the iPhone on my business account!!! (Boy do I love this thing already

) AT&T reps were most confused on Monday, the first day, but activating the phone on a business account was pretty easy. Here is what you have to do if you are
an existing AT&T business customer:
1. Call AT&T business services (800-331-0500) to add the iPhone data plan of your choice to your line (you must be authorized to do this on your business account of course)
2. Purchase the iPhone
3. Swap the SIM card out of your current phone with the one that shipped in the iPhone (this is critical as iTunes will not let you go forward as a business account with the new SIM card shipped in the iPhone)
4. Connect to your computer and follow the prompts in iTunes, selecting the business customer option
Within a few minutes you should be good to go. The only hang ups I had was waiting for visual voice mail to kick in which took about 30 minutes and required a call to AT&T.
The data plan rates are as stated in this thread, but there is the $25 monthly discount through the end of 2008.