Problems with service reach and operator detect

[anthaet]

I have problems with reach and finding operator in my LG G2.

I bought the phone on last vacation in USA. It has AT&T logo on it so it was meant to work with this network. I used it with SimpleMobile and it worked without any problems.

When I returned to Europe problems had started. My reach is very low, and phone sometimes cant detect operator (then I can call only emergency numbers).

I found that I have to change network mode to 2G/GSM. But I dont have any such option in network settings.
All settings > Tethering & networks > Mobile networks, and I have such options, but no „network mode”:


Someone has any idea what can I do?

 

[B. Diddy]

Welcome to Android Central! What happens if you tap Network Operators? Are you sure your correct network is selected there?

 

[anthaet]

Thank you for reply.
In "Network operators" I have two options: "Search networks" (here I have my operator and few more but I can select only my one) and "Select automatically" (when I tap it I have information "Automatic registration..." and then "Registered on network."