Lg G3 850d networks

Hi, I recently bought a LG g3 smarthphone and I found out that it's an AT&T version phone, but thankfully it's unlocked. My problem is, that it doesn't get any mobile network. In the setting it says that the Mobile network type this device can use is EDGE, but my local carriers can only provide LTE, GSM and WCDMA. I've tried to solve this on my own, but without luck. The solutions with 3845#*850# or similar codes just woun't work, when I choose any RAT it says: "succsess", but it doesn't change a thing and when I choose LTE only mode the phone blocks my mobile connection and says: "Restricted access changed: Data service is blocked" .
I really need any help, because I cannot see myself using a mobile phone without mobile internet. BTW, my location is Estonia.