Unlock codes are available online from a number of different sources. These sources take the phone's IMEI and PIN and generate an unlock code for you. The prodedure takes just a matter of minutes and generally costs about $10. Doing an online search for "BlackBerry unlock codes" should return some options for you. Other members might even add to this response with specific services they've used in the past and who are known to be trustworthy.
Bell is a CDMA network. ACDMA network mobile cannot be unlocked to use with a GSM connection. Only GSM mobile can be unlocked to use with any other GSM connection. You can unlock a GSM mobile using unlock code. All the best mate.