1. On your BlackBerry, go to Setup >> Options >> Device >> Advanced System Settings >> SIM Card.
2. At that screen type MEPD (see note below) on your keyboard. A new menu will pop up and show you information similar to one our our devices:
SIM = Disabled
Subset = Disabled
Service Provider = Disabled
Corporate = Disabled
If your BlackBerry has a SureType keyboard (71xx and 81xx devices) you will need to double-tap the P, so the actual keys entered become M E P P D.
3. If your device is “unlocked”, Network should report either Disabled or Inactive. If it says Active, the device is still locked to that carrier.
Another method to determine if your Blackberry is “unlocked” is shown below:
1. Power-off your Blackberry.
2. Remove the back cover and battery pack.
3. Carefully slide-out the T-Mobile SIM card and replace it with a SIM from another carrier.
4. Insert the battery pack and reinstall the cover,
5. Power-on your Blackberry.
6. If your device is locked to T-Mobile, you will receive the message
“The current SIM requires an Unlock Code. Enter the Network MEP Code.”