AIM Feature on LG CU400

All right, so I've paid for unlimited text messaging. AT&T says that signing into AIM is free if I access it via the icon on the phone and NOT through MEdia Net, and that the messages are SMS (meaning that since I have unlimited text, these fall under the plan!)

When I do this, the little globe still pops up in the top left-hand corner, just like it does when I connect to the internet. I don't have a dataplan, so naturally, I feverishly cancel whatever I did to make the little globe appear. Am I doing something wrong on the phone, or am I interpreting things wrong?

Edit: I have Unlimited Messaging for Families

Every time a data connection is made the indicator will be displayed. Whether you will be charged is determined by the application you are using. It would be simple to execute one session and check OLAM later to see if you are charged for data usage.