How to Change Huawei E220 Network Preferences on Mac: 3G or 2G

I have Huawei E220 modem runs on my mac. By default this modem use automatic network detection for 3G or 2G, if there’s enough 3G (HSDPA/UMTS) signal the modem will works on 3G, otherwise if 3G network signal is poor it will detect 2G (GPRS).
Why it is so important? In my place, 3G network [...]