Well, technically, you would have to find a way to get the frontline customer care agent convinced to connect you to a real technician. They usually can tell you what frequencies / bands / towers are being used in your region. Maybe this
wireless network charts can help you to determine if the phone supports the needed frequencies?
Back in the days, there used to be maps out there on the internet, showing what frequencies are being used in different states and cities. I am not sure if those still exist and I didn't have enough coffee yet to research this. :)