Step by step guide for new user
At first, you need to know the phone model and firmware version.
To check this, you can go to settings - about the phone - program information - basic version (various phones may vary) or connect the phone to your computer and click "read information" in the utility.
Then check the operator and lock type.
Insert a SIM card of another operator. The phone will tell you that it is locked ("Invalid Sim Card") or ask for codes.