[Q] How to Unlock Samsung Galaxy S3 & S3 Neo

I have Samsung Galaxy S3 (Model No - GT-I9300 ) And Samsung Galaxy S3 Neo (Model No - GT-I9301I ) , I try to unlock the phone using *#197328640# code number, But no any responded in that devices. :(
Galaxy S3 Android Version is 4.3
Galaxy S3 Neo Version is 4.4.2

Please Help me for Unlock the country lock free of charge. :confused:

Any one know about this please quickly help me.