First, check the SIM lock status in Service Menu - from the Phone dialer app tape *#*#7378423#*#* Service info ► Sim lock

o Network 5

x Network subset 0

x Service provider 0

x Corporate 0

x SIM 0

Normally, Sony Ericsson phones comes only with a network lock as active.

o Network 5 - the phone is Network locked and you have 5 attempts to enter the unlock code. If there is a 0 beside the category where a lock exists, then it means that your phone is hard locked and you can't unlock it by code.