So what's different about Oz modems?
I'm using a G300 in NZ with the Huawei factory Chinese B926 rom. I was getting good Vodafone service around town with data connection showing a 3 or H, and Settings -> About Phone -> Status -> Mobile network type: UMTS:3
Then I went 50kms out of town and lost everything, not even 2G available where I could see the tower. I searched this forum and found about the "Testing" menu, dial *#*#4636#*#* -> Phone information -> Set preferred network type was at WCDMA only
I changed this to GSM auto (PRL), rebooted, and now get good service in town and country both 3G and 2G. I think this happens 'cos Vodafone NZ are using WCDMA 2100 in town and have expanded 3G service in rural areas by putting WCDMA 900 alongside 2G/GSM 900. Discussion so far in this thread makes me think my phone won't work in Oz unless I change to LA modems, but I'd rather not because I will be going to China with it.