I bought a used phone from Romania and since the beginning it have not been able to find 4G network

Now since a week ago it will not use 3G either, just says "not registered on network" unless i force it to go on GSM, but the SIM works just fine in another phone.

The phone is used by a kid who is mainly using it to play and sometimes watch movies on youtube while being connected to a wi-fi, but biggest problem right now is that he can not call at all.

According to [ Login above or register to see download links. ] the IMEI says "The numbers 05 or 50 indicates that your galaxy smartphone is manufactured either in Brazil, USA or Finland".

I would assume that this would give problems with 4G to begin with, but that does not matter, the issue is that 3G is not working either.

Should I try Romanian or american ROM? or should it still work with nordic ROM?

I tried checking some of the hidden codes, but i find nothing that can test the networks.

This is what ServiceMode shows if it gives you any hints:

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Anyone have any idea about what I can do to get the 3G back?

I switched the antenna cable, but no change.
I also reset cache, no change.
I also tried to just enable/disable flightmode, no change.
Changeing networks makes no change until i choose only GSM, where it works fairly ok.

Thanks for any help!