hey, to see if you phone is actually unlocked, do this:
1. On the Home screen, click the Tools icon. The Options screen appears.
2. In the tools screen, select the Settings icon.
3. Scroll to SIM Card and select it. You should see the phone number and the SIM ID number.
4. Type 'mepd' to display the first five levels of SIM locking. T-Mobile uses network locking so the Network should display Active. All other states should display Disabled

And read through this thread (and other threads, I searched for "lock setting" using the search button at the top of this page ) for more info...
Unlocking the Berry...