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Hi everyone I'm Salvo nice to text you all. I have a problem with my Sony z5, I insert my sim inside but I have no service!! Anyone can help me??
This might help.
Go to settings> More>Mobile Networks>Preferred Network Type>select LTE/WCDMA/GSM.
Hi @Salvo95, welcome to our community!
I'm sorry to hear about that. 
Is this something that has started to occur very recently, for example after you updated your phone or installed a new application?
If your SIM card has a PIN code on it that you need to enter to unlock it each time you start or restart your phone, is this something that you are asked to do? That way we can see if the phone recognizes the SIM card.
What @Akashv0444 recommend is a good place to start, you can try the different network modes and see if you are able to get service on 2G (GSM) or 3G (WCDMA). You can also run a network search in Settings > Mobile networks > Network operators and when the search is done, tap on your home network (marked with a house icon) and register on the network.
If you still can't get service in your phone, try with another or a new SIM card. If one of your friends, colleagues or family members have a nano SIM card as well you can always ask them if you can borrow theirs and see if you can get a connection the network that way.
Let me know how it went! 