FoF is going to New York for a few months, so will use a local SIM in their phone. They'd still like to keep their XT phone number ringing, so they were thinking about taking their old GSM phone with them, and using it with their XT SIM.

Obviously that won't work in NZ, but it should overseas, depending on the local networks in use.

So the question is, which Networks in the US do XT SIMs roam with? And what networks will the phone need to support for them there?

The telecom site is scant on detail, doesn't mention which networks, and frequencies are required...