Wifi 3G ?

I've never heard of that, I think you are confusing WiFi with cellular 3G technology. Since each cell phone carrier deploys their technology a bit differently, often on different and proprietary equipment with unique drivers, I'd suggest you contact the cell phone carrier that you plan to use, and ask them if their version of 3G works with Windows7, and what is required to make it work.

Bear in mind, most of the cell phone reps aren't expert technicians, they are out to sell you something.