Ok so this issue has plagued me since the start of my N9 ownership. This problem existed from PR1.0 for me and it drove me nuts.

I was on pr005 from Australia.

I decide for pr1.3 to flash to pr001 global, which is vanilla. I also got a new micro-sim from t-mobile.

At this point My service is better on my N9 than any other phone I have.

This seems to be the way to go... Also if you're looking for only 3g service it's very hit or miss everywhere. If you set it on dual or gsm, it's solid as a rock.