Okay, I have a Windows Mobile Smartphone. I want to get internet and email on my phone. I don't want to pay $20 every month to do this.
It is possible to do it with the old $5.99 internet plan. Here's what I had to do:
WARNING – This requires messing around with configuration files on your phone. You can render your data connections useless if you do it wrong.
That said, I haven’t had any problems with this method.
Get the $5.99 internet plan on the account. This required changing my phone on my.tmobile.com to something other than a smartphone. I used a V3 Razr, as that's the phone I used to have. -Note that it may take 24 hours for this to go active on your account.
Delete all connections and proxies set up on the smartphone.
Install the cab from this page: http://forum.xda-developers.com/showthread.php?t=395203. Get the tmobyjoe599.cab file, not any of the others.
Reboot the phone, and tada, your connection is active!
Now you can set up to sync with Exchange, surf with PIE, and do all kinds of stuff. Please note that Hotmail and Windows Live will not work. Some other applications can have their proxy/connection settings set manually to get them to work.
Sometimes this works, sometimes it doesn't, so your mileage may vary. If it doesn’t work, try rebooting your phone. If it really doesn’t work, try deleting all your proxy settings and reinstalling the cab file. If you totally screw everything up, you can always hard reset :)