The short answer is, now a day most newer modern models of mobiles phone devices will work anywhere in the world if it’s unlocked.
The long answer is, if you want to know for sure, and you want to check it yourself instead of calling the provider and others. What you need to do is below which I found work for me. Taking the Amazon Fire Phone for example. Does Amazon Fire Phone Unlocked from USA work in Vietnam?
- Make sure the phone is unlocked. The best way to check is insert another sim from another provider, such as if you have AT&T, you can insert T-Mobile Sim from your friends or got one lying around, it does not need to be active sim. What we’re checking here is the Phone will show a different Provider, in this case T-Mobile should up with T-Mobile Sim etc.
- Check your Phone GSM network frequencies supported. Then check the Country you’re going to Mobile Network frequencies supported by whatever phone company in that country. Ensure the frequencies matches. For example the the Amazon Fire Phone support GSM bands 850, 900, 1800, 1900, and the country I’m traveling to is Vietnam and one of the mobile network there support 1800, then that is good enough.
So there you go, no need to contact your provider or the country mobile network phone provider, you can check it yourself 🙂 Works for me 🙂