Q: my phone is locked, and I can't remember my pass code. How can I unlock my phone?

You will have to restore it to remove the passcode, as explained here: http://support.apple.com/kb/HT1212.  If it was running iOS 7 with Find My iPhone enabled, you will have to either force it into recovery mode to restore it, as explained here: http://support.apple.com/kb/ht1808, or remotely erase it using Find My iPhone on icloud.com.