How did you try to unlock it? A lock is usually a software feature. Did you try to hit it with a hammer?
Read the warranty terms. Accidental damage or tampering with the device is not covered.
Service and Repair - https://selfsolve.apple.com/ - Repair options (requires hardware serial number)
Service Answer Center - iPhone - http://support.apple.com/kb/index?page=servicefaq&geo=US&product=iphone <-- enter correct country once on page.