After trying JSanders advice (which is ace
), you will want to read this:
Your BlackBerry does not have a PUK. Your SIM card does. Only your service provider can give this to you. It was also likely printed on the holder in which your SIM card came when you purchased it. If your service provider will not provide it to you, you will need to get a replacement SIM card. Doing so will not affect your phone number or services.