All models of BlackBerry
1 - Go to the menu, then Settings Menu -> Select Advanced options => and then Sim card.
2 - While holding down the SHIFT key, type MEPD or (MEPPD combines for Vodafone)
3 - You should now see the five categories listed lock.
4 - While holding down the SHIFT key, type MEP2 or (MEPP2 handsets for Vodafone)
5 - Release the Shift key.
6 - You are now invited to enter the Network MEP code (it will also be the number of attempts left)
7 - Enter the code
8 - Enter Return / Enter
9 - The device must be unlocked
T-mobile:BlackBerry Models1 - In Home screen, click the Tools icon. The Options screen appears.
2 - Select Settings icon.
3 - Scroll to SIM Card and select it. You should see the phone number and and identification number of the SIM card.
4 - Type ‘mepd’ to display the first five levels of SIM locking.
T-Mobile uses the network to lock network should display Active. All other states must be disabled
note: For the Blackberry 7100t you press "P" twice when entering the mepd 'and' mep2 "for steps 4 and 5..
5 - Type ‘mep2′ to display the dialog box asking for the unlock code (Press the Alt + 2 key to get the number 2)
6 - Enter the unlock code network
7 - Press ENTER and reboot handheld.