I know that this a late answer, but... didn't ANYONE thought that the phone is SIM-locked?!?!? It's obvious! Exclamation Mark before the provider means "no acces to this network"!
Sorry, i meant PF or antenna switch. You can check the diagram of the fone using serch button. Usually u should start by changing the PF, if the network is not stable, then u change the antenna switch. You shall need the hotair pump