Question [Q] Change baseband for Next G Network

Hi there I was wondering if anyone has successfully got the Motorola milestone 2 to operate on the Telstra Next G network I have tried the brazil sbf which is 850/2100 umts it connects for a few seconds on the 3G network then totally drops I can get it to connect to the gprs network and it will hold that connection but not the 3G Telstra must have a different frequency on their 850 network? I would really appreciate any support or ideas thanks for your time.