Hello, I have this same problem, buy N900T [stock n900tuvucnb4] in US, to use in Europe, Poland.
3G band is working, calling and internet, but 2G is not, no signal ;/
I instail custom rom from n9005 [alexndr.n9005xxugng1] and custom kernel [aurora kernel r11].
Phone have 2g signal, is conecting to the carrier but i can't make a phone calls and sms, I dial a numer but noting hapend, no signal.
Any advice ?