Than its going to 2G mode.
I tried following method and it has been working great since than.
Connect wingle to ur laptop. By default 2G/3G option is selected, which cannot be changed. For this purpose you need to cover your evo wingle either with wire mesh or some clothing so that it may not find any network only than you will be able to change it to 3G mode only. Do it and save it. Remove mesh or clothing covers and let it connect. Once connected you will not be able to change it back and it will keep on working in 3G mode forever until you reset it manually.