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

[ad#inline-single] 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 signal are weaker than 2G, so if the modem detect automatically, I can not use 3G instead.