Restriction code mostly asks for Nokia Mobile Phone@!!!Your Phone is Nokia?what Model,?Because it locked to network so it asking for restriction code...
If your Nokia mobile phone displays Phone Restricted with an Undo option and selecting Undo results in an Enter Restriction Code error, your Nokia mobile phone is Network Locked. This means your Nokia mobile phone has been restricted for use on one specific network and a Restriction Code or Unlock Code must be entered before the phone can be used with alternative networks.
You can get the Restriction code from here