Unlock Description:
Sony Ericsson unlocking via IMEI only.
Simply send the IMEI and receive the unlock code. NCK provided.
To check the counter of your phone:  Please check that there is enough attempts to enter the unlock code into your phone.
With a Non accepted simcard  start up the phone. When the screen says "emergency calls"
1. Start up the phone and press the Menu key ( ) and Back key ( ) as follows:
2. Pressing Key Sequences: Menu Back Back Menu Back Menu Menu Back
Note: Please make sure the phone have SIMLOCK when pressing these keys to get into the Service menu.
Also You can check there is counter of wrong code is blocked.
OR
press *#*#7378423#*#* and access the service menu
You will see a menu:
Example:
Network    10
Network Subset   10
Service Provider   10
Corporate 10
Sim   0