Follow the following instruction to unlock your mobile...Get the following instruction here
Mobile Unlock Guide : Get unlocking instructions for your mobile phone
1 - Switch on your Blackberry 8310
without any Sim card.
2 - Go to
Options.
3 - Select
Advanced Options.
4 - Select
SIM Card.
5 - Hold the ALT Key while typing in MEPE or MEPD or MEPPE or MEPPD ( not case sensitive ) ( you will not see text appear on screen while typing ).
6 - You will then be presented with a prompt "
Enter Network MEP Code". Type in the Unlock Code and press in the track wheel / jog dial to confirm,
7 - Your Blackberry 8310 will now be unlocked.
And get the unlock code here
Mobile Unlocker- Unlock Your Phone