Share your experience!
Hi @Marcous, welcome to our forum! 
To turn off the demo mode, start with opening up the Phone application and type in *#*#73556673#*#*.
When you have done this you should be at the home screen again and the demo mode will be deactivated.
Let me know if that helps! 
New ı buyed sony xperia xz mobil Phone but dost read ana sim card howe can ı solve the tıs problem ı do * # * # 73556673 # * # * code and reastart mobıle stıll not read sımcard
ı waıtıng any helps
Hi @LandSurvey, sorry to hear about this. 
If you are using a new SIM card, make sure that it has been activated by your operator. You can also try with a new/different SIM card, for example, if you can borrow one from a friend, colleague or family member.
On the link below you can see how to insert the SIM card in your device.
https://support.sonymobile.com/global-en/xperiaxz/userguide/assembly-ss-content/
Let me know how it goes!