I have a roaming SIM in my second sim slot. As I travel around it switches to the best available network - that's it's job, it can't be locked to one network. At least, it could, but that would make it useless.
However every time it switches network I get a 'Service Message' that displays over anything I'm doing and has to be dismissed.
I can't seem to find any option to prevent it - anyone got any ideas?