Here comes another Hardware Post: T-Mobile MDA Bluetooth Modem Setting
I am currently in the MSFT Conference room, and like many of you know - MSFT does not provide open WIFI...so I was tinkering with my MDA and though things would be easy...
After a quick [20mins] on hold with T-Mobile tech support - the phone number needed to be dialed from the modem is *99# and it's good to go.
Step 1 - Pair the device with the laptop/computer, you will consume the DUN service from the MDA and a 'Standard Bluetooth Modem' device will be added to your computer.
Step 2 - Go to Network connections and Add New Dial-up Connection, in the phone number type in: *99# [this will only work for TMobile customers with GPRS service]
Enjoy!