Can i use iphone 5s (Sprint) in Vietnam

Call Sprint and get the device unlocked. Make sure you don't lose your Sprint SIM when you come back to the US. Unlocking a Sprint phone will only unlock for international usage not for within the US

 

You need to contact Sprint to unlock your phone. If you're buying a phone from ebay, there is a good chance that Sprint will not unlock it because either the phone is blacklisted or because you are not a Sprint customer. If it is not unlocked, you can't use your Vietnamese SIM.

Avoid causing problems for yourself an buy a GSM unlocked or Verizon iPhone.

 

Here are the rules.

1. Establish service with Sprint (it cannot be an ASL (Account Spending Limit) account)
2. Maintain service with Sprint for 90 days
3. Pay your bill on time
4. Call Sprint, ask for international unlock

If you CANNOT meet ANY of these requirements, Sprint will NOT unlock your iPhone for international use.

There is NO third party unlock, either for international or domestic use. ONLY Sprint can unlock your iPhone for international use.

If you have purchased already and cannot meet #1 and #2, congratulations you have just bought yourself an expensive iPod Touch!