Well, ice, what do you want first the good news or the bad news? You can definitely get Internet access on your phone for t-mobile. (I should know, I also have an SE with t-mobile). Unfortunately, it is going to cost you. I tried everything from jinxing the settings to playing around with different options but no luck my friend. What you will have to do is set up an Internet access plan. It usually doesn't cost too much and I included the link. I have unlimited Internet access, since it doesn't cost very much, I'm paying under 10 bucks for it.It should be about the same, but on the tmobile site I inculded, ou should be able to see how much it will cost you. I also included the links for you to set up other things with sonyericsson.
Let me know if this takes care of you.
P.S. check out Esato.com. You can get a lot of info, as well as software to improve your camera, music player etc. Just be careful with what you download though, firmware is an unforgiving mistress.