Locked sim card

May i ask what it says when it asks for a code as it may be your sidekick is not unlocked at all. If it is however unlocked, and i appolagise if i am wrong, it may be asking you for a phone unlock code which the previous owner put on it. You would need to contact the previous owner for this code as the mobile phone provider will NOT reset it for anyone else as there will be a security question to answer before they will reset it!!

Hope this helps

Karlos