iPhone 3g firm 3.1.2 with Tmobile, won't work, please help!!

[thew47]

I have a 3G iPhone with firmware version 3.1.2 on it. I just downloaded Swirly 2 and I can only send pics (MMS) to myself. I tried to send to other people, but it does not work. I do have the green "M" in the corner, so it should be working. PLease help!!!!!!!!!!!