How to unlock bb 8800 t-mobile - RIM BlackBerry 8800

Follow the instructions mentioned by marbleann & get the code from unlock4u

Call T-Mobile up and tell them you want to unlock your phone because you are going overseas if they ask, but they won't and they will unlock it for you. They will send you the code to do it. T-Mobile has no problems unlocking phones at all. Here is the way you can unlock the 8900, which I used for my phone. This might work for the 8800. Just get the code from T-Mobile

1. Press the Menu key
2. Scroll to and select Manage Connections. Select Turn All Connections Off.
3. Press the red end key or the Escape key to go back to the Home screen.
4. Scroll to and select the Options icon.
5. Scroll to and select Advanced Options.
6. Scroll to and select SIM Card.
7. Type MEPD Note: When typing in MEPD the letters will not appear on the screen. This step opens up the personalization on the device.
8. Type MEP then hold ‘ALT” key and type number 2. Note: When typing in MEP ATL 2 the letters/number will not appear on the screen, this step open up the “Enter Network MEP” box.
9. Enter the unlock code.
10. Press the trackball (“Code Accepted should display)
11. Press and hold the red End key to turn the hand held off and then back on.
12. Once the device has powered on, follow steps 1 & 2 and restore connections.