How do you read messages?

[itsme]

I see on the mobile phone option you can read and write messages. But it's always not available. I have my 910 linked to my Cingular 8125 for both data and voice. Traffic and everything work fine I was just wondering how to use the message function. I just upgraded my plan to unlimted data from my unlimited internet plan. For traffic does it use the internet or data. Thanks for any help.