I have the same problem, I investigated and discovered that the fault lies with the cloud service xiomi.Phone process force closes on Settings/Mobile network/Network operators, this was also happening on 2.7.13.
Also, can you see anything wrong with your credit? I found that my phone was sending international text messages to +106571203855*** multiple times and at different periods for a total amount of more than 15,00 €. I told H3G Italy about this and they said they will investigate and report back to me, but that prefix doesn't seem to even exist! Delivery notifications are off (but they count as a standard SMS) so that doesn't seem to be the problem. Is it MIUI?!