Phone SIM unlocking is something that a few people just panic about, and it's all because they are unaware about the way to do it. All you need to know is a couple of important information about SIM unlocking procedure and you are good to go.
So, the first thing that you need to see is whether the phone is actually locked or not. For that, you need to first insert another network SIM card in your Sony Xperia XZ3 and wait until you see if there’s any notification that further says “SIM locked”.
If it does then for sure it is locked but in case it doesn’t, then there must be some another problem that you need to get checked at any mobile store.
Now, that you identified that your phone is sim locked you need to order for an unlock code and that you can do by dialing *#06# on your phone to get the unique 15 digits IMEI number.
Once you get that you are supposed to share that information along with the details of your current operator name, and the country that you are living in, in order to verify it.
After a few minutes they have verified your documentation details you will receive an email with an unlock code and a couple of important information on how to use the code.
The instruction in the mail says that you turn on your phone, insert another network SIM in it and wait for a while. You will see a message saying “ENTER PIN”, and all you got to do is enter that unlock code in your Sony Xperia XZ3 and restart the handset.
You will have your phone functioning normally within seconds after you follow the above-mentioned steps. You can order these unlock codes from unlocking firms such as Unlock Unit. They run these services and have been successfully providing these for a long time.