I use the app from the Apple store.
But you said the IM app from Apple. And I assume you mean the App Store.
The one in the Apple store is not made by Apple, but AOL. The one made by AOL connects to the internet through either Wi-Fi or your Cellular network, which is covered by the $30 data plan (note the use of the word DATA). The one built into the phone allows messages to be sent to AIM users, but as a text message that is processed and sent over the Internet. That is why it applies as a text message.
IM is instant messaging.
AIM is AOL Instant Messenger.
IM sends texts.
AIM sends data.
And, as others have said, the fact that the iPod touch can use the SAME app as the one on the iPhone proves that it uses DATA not Text Messaging to send messages.
The iPod touch is not linked to a text account, yet users can still text on the phone IF they are connected to a wireless network, which has nothing to do with AT&T.
Maybe if you re-submit that letter to the woman at AT&T stating it was the AOL AIM app that you use, and that uses data (as proven by its use on the iPod touch), she may take the charges off.
However, if she says that you did not use that app to send messages to AIM accounts, then there is nothing you can do.
Another thing is that you said that it shows up as AIM/IM on the bill. The use of applications on the iPhone that use data do not show up individually on the bill; they all fall under the category of "DATA". That $30 charge added to your bill is UNLIMITED data transfer, but not messaging. You can send as much data as you'd like, but once you go over your limit in messaging, they will charge you overages.
