Network Problem in Sony Xperia Z C6603

Hi everyone, this is going to be my first post on xda. That's why just pardon me if the thread has been posted in to a wrong section. So here is my problem, a friend from the UK brought me a Sony Xperia Z which was bought with a contract from Three almost 3 years ago. I'm living in Turkey and I know that government locks the mobiles after a month if they hadn't been registered and consequently my sony's imei has also been locked. After that I was going to register it with my passport to use it but a point stuck in my mind if the mobile has a carrier sim-lock too. I made some research on the net to figure out whether there is or not and how I can get out of this. I'm going to attach a screenshot of code "*#*#7465625#*#*". As far as I understood, there is no simlock, however, it has been locked by the government due to lack of registration. Please make some suggestions :)

Thanks in advance.

*s30.postimg.org/7eidefq7l/Screenshot_2015_08_10_13_00_52.png