I used this guide to get the national roaming working.
http://forum.xda-developers.com/showthread.php?t=1483419
only step 11 is a bit different with our Mi2. In the manual it says:
11. Now the complicated part:
Search for the following lines
if-eqz v0, :cond_49
if-nez v1, :cond_4f
if-nez...