Most blackberry phones are
locked to certain networks and
this makes it impossible to use
them on other networks or with
a different SIM card. You can
have a blackberry phone bought from Verizon Wireless in the US
but might want to save yourself
that high roaming cost on your
visit to UK but you definitely
can't use it with other carriers
like Vodafone or AT & T. Unlocking your blackberry
phones gives you the freedom to
use your phone with all network
carriers in any country, changing
your SIM cards at will without
being bond to a contract. Apart from this, unlocked phones are
much more valuable in the phone
market, you can visit Ebay just
to see exactly what I'm talking
about. The steps given in this post on
how to unlock your blackberry
phone isn't a simple process, but
it's not that hard either. I did it
with a Blackberry 8120 so why
can't you? Before you proceed, you can call your network
carrier and request for the
unlock code but I'm not so sure
they'll give you if it's a phone
bought on contract. You've got
to find a way to unlock it yourself and you need the
following tools to get this done: 

1. Latest Blackberry Desktop Manager 2. Microsoft .NET Framework 3. Your Blackberry phone's operating system 4. MFI Multiloader setup 5. MFI Multiloader
-part1 -part2 -part3 -part4 -part5 -part6 -part7 -part8 You've gotten all the softwares,
right? Now lets get started!
Please note that you're doing
this at your own risk and I'm not
responsible for any damage that
might arise from this process. You might lose your warranty if
you continue...so think about it. If
the you follow the process
carefully, you should be smiling
at the end though when your
blackberry phone is unlocked. :) Now here are the first things
you must do before starting the
unlock process: A. Make sure your Blackberry's
battery is charged to at least
50% B. Make sure you do full data
back-up before doing anything.
You don't actually need this if it's
a new phone. C. Remove your SIM card, turn
off radio, turn off Bluetooth,
turn off Wifi or any
connection on BlackBerry. D. Install Blackberry Desktop
Manager E. Install Blackberry OS (be sure
the Blackberry operating system
you're installing corresponds to
the phone model!) F. Install MFL Mutiloader setup. G. Extract all the parts of MFI
Multiloader and copy toC:\MML, replacing the content of the
existing conetent in the MML
folder there. H. Go to C:\Program Files\Common
Files\Research in Motion
\Apploader and delete vendor.xml I. Disconnect your computer from
the internet. Be sure you performed each of
the 9 steps above without
omitting one, OK? Now, let's
proceed. 1. Go to the desktop and run MFI
Multiloader. 2. Make sureLogging and Database is off. 3. Now connect your Blackberry
phone through USB and hit the
start button on MFI Multiloader 4. Wait till it shows PASS 5. Your BlackBerry will should
show1 on the screen 6. Disconnect your BlackBerry
from PC and close MFI
Multiloader. 7. Type START on your phone. After finishing this operation,
your phone can show you
message like "error 507" or "no
application linked"...don't worry,
it's "normal". Your phone is
unlocked now, but you'll need to reinstall the OS and set it up. 8. Open Blackberry Desktop
Manager, connect your phone
and click on Application Loader 9. Select "Add/Remove
Applications" 10. Choose applications and
extras, and click Next 11. Wait until Blackberry Desktop
Manager finishes the whole
operation. It might take up to
twenty minutes or more. Please note that you're doing
this at your own risk and I won't
be held responsible for any
damage you cause to your
phone but if you've got a
problem with the process, I'll help if I can, only if I can. By the way,
some issues can arise after this: * Device can't connect on MFI
Multiloader.
-Copy BbDevMgr.exe from the C:
\MML\bin\, and overwrite same
one in the location C:\Program
Files\Common Files\Research In Motion\USB Drivers\ * MFI Multiloader shows FAIL.
- You can get this message if
your MFI Multiloader version is
older. Download newest, and just
repeat process. Also be sure you
disconnect fro the internet before doing it. 

Source www.cube.lefora.com