Getting Charged for using IM Feature?

Hey everyone, I just joined at&t and have a Samsung Propel phone.  I am under a family plan that has the "Messaging Unlimited for Families" feature added.

Two days ago I used the IM AIM program that is built into my phone.  The next day I looked online and saw I was charged data for using it, even thought I thought it was free under my feature ($3 worth!).  I stopped in a store yesterday and they said as long as you use the AIM built in the phone it should be free.  Thinking something else strange might have happened I used AIM again last night.  I did not send or received IMs just was available.  I would only recieve some notifications if someone came online.  I looked this morning and again I was charged, and the times fit when I was logged on.  On the Account Overview it shows this:

11/08 11:07 PM wap.cingular Internet/MEdia Net Sent 6KB 11/08 10:51 PM wap.cingular Internet/MEdia Net Sent 8KB 11/08 10:44 PM wap.cingular Internet/MEdia Net Sent 4KB 11/08 10:33 PM wap.cingular Internet/MEdia Net Sent 8KB 11/08 10:27 PM wap.cingular Internet/MEdia Net Sent 4KB 11/08 10:21 PM wap.cingular Internet/MEdia Net Sent 4KB


What is going on here?
Thanks for any help!!