How to use my US iphone 5 in Vietnam network?

I want to send an iphone 5 to vietnam for someone to use and i want to know iphone 5 can do that,? Sprint, tmobile, verizon and att? Does it matter which carriers able to? And how do i unlock them or what process?

  • Would my iPhone 5s work in vietnam? I just got an brand new iPhone 5s yesterday. I'm going to vietnam sometime soon and I want to know if my iPhone would work over there. I'm with Verizon and my phone is 4g capable and I get 4g in some areas here in san jose. Would my iPhone work in vietnam?
  • Wi-Fi on iPhone keeps saying unable to join network (my network name)? How can I fix this! It's been like this for a week but it works on my laptop fine. I tried unplugging it for a few seconds, I tried resetting network settings, I tried turning my phone off then on again, and I know I'm typing it right. I even typed it in upper case AND lower case. Does anyone know how I can fix this?
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