Another really strange thing: among the "preferred networks", at the last place, there is this code "316 01", and if I'm not wrong it's Nextel, the iDEN network in the USA. Not very useful on my GSM/UMTS phone!
I tried then to call myself from my 3 number... on Travelsim phone it didn't appear my 3 number, but this one: +372.6868097, which is a geographical number, Estonia, Tallinn district (new digital number). If I try to call it, it rings!
So there is a triangulation also for incoming calls, in fact I couldn't hear any free of busy tone on the 3 phone until I accepted/denied the call on the Travelsim phone.