I will be traveling to the US soon and I will be expecting to make phone calls abroad from the US. Is it possible to phone abroad from the US with a Vietnamese SIM card with a Vietnamese carrier (since that is the SIM card I currently have)?

If not then when I do purchase a SIM card in the US, what other requirements, besides dialing the correct country code syntax, will be required for me to phone abroad while in the US?

Furthermore, if I were to buy a SIM card in the US, how will I enable access to 3G on it? Will this require registering with a post office/carrier centre ...etc? Thanks.

  • 2
    You local Vietnamese provider should be able to tell you whether you can use your SIM card in the US. The roaming fees for this service are often outrageous, though.
    – DCTLib
    Commented Apr 20, 2016 at 11:55
  • As for your other question, it is already answered here: travel.stackexchange.com/questions/46771/prepaid-sim-card-usa
    – DCTLib
    Commented Apr 20, 2016 at 11:56
  • Make sure the frequencies are compatible, and be aware 2G GSM is being phased out.
    – gerrit
    Commented Apr 20, 2016 at 13:04
  • 1
    note that the US is incredibly backwards about "overseas! phone calls" compared to futuristic countries like vietnam and switzerland, etc. Very popular in US are silly "phone cards". So, you need to phone somewhere incredibly exotic like Mexico! or England! Almost anywhere (petrol stations etc) you can buy a "phone card" for say $10 or $20 (they are marketed for "calling different countries"; you might find an "Asian!" card or indeed "Vietnam!" card, etc). You basically call an 800 # and then call through to your destination. The rate is "moderate".
    – Fattie
    Commented Apr 21, 2016 at 15:13

1 Answer 1


It is probably possible to make calls from the US to Vietnam, but it depends on your provider. (e.g. Viettel - yes, Vietnamobile - not possible for prepay customers).

Before you go, you'll need to turn on roaming. Your provider will have instructions for doing this - searching for Viettel Roaming or Vietnamobile Roaming got me what I was looking for, so I guess doing the same for Mobifone or Vinaphone will do the same. You could try searching for CQVT [your mobile provider] as well, which seems to mean Roaming in Vietnamese. They'll probably want you to have a fairly large chunk of credit on your phone, certainly in the hundreds of thousands of VND.

Before you turn on roaming though and call away, as was pointed out in the comments, it will be expensive. Viettel charges you somewhere in the region of 33000 VND/ minute to make calls from the US to Vietnam (that's about $1.50 right now). On the other hand, that's still cheaper than the $3.99 / minute that T-Mobile USA for example will charge you to phone home. Your cheapest option to make calls home is likely to be to use data on a local SIM, and (again from the comments) the question as to how you can do that has already been asked.

It will also cost you a lot of money to receive calls - it looks like Viettel would charge 11000 VND/minute for example - so bear that in mind as well. On the upside, it should at least be free to receive an SMS.

Finally - to dial an international number, you just dial + followed by the country code, so for Vietnam that's +84 (you also leave out the leading 0 of the number).

  • thanks mate apparently the whole roaming business seems incredibly expensive so I think I'll pass on that and stick to buying a local SIM when I get there, possibly a pre-paid one, though I'm not too sure how stuff works in the US regarding phone call charges
    – tsp216
    Commented Apr 21, 2016 at 10:30
  • 1
    Also, data roaming is often prohibitively expensive as well, and of course usually counted outside of any in-country allowances.
    – jcaron
    Commented Apr 21, 2016 at 11:18
  • Unless you really require to be able to call while "on the go", I would recommend exploring VoIP options, such as Skype, which will most probably be a lot cheaper per minute than whatever you may be charged for using a pre-paid SIM card. Also note that in many countries, not all pre-paid SIM cards allow international calls.
    – jcaron
    Commented Apr 21, 2016 at 11:21
  • @jcaron - thanks! I've updated the answer to hopefully clarify that a local SIM is the way forward for data.
    – EdC
    Commented Apr 21, 2016 at 11:32
  • Ideally, I'd say the better way is Wi-Fi. Not sure what the deals are on data on prepaid SIMs are nowadays in the US. Definitely better than roaming for sure, but may still be quite expensive compared to contracts.
    – jcaron
    Commented Apr 21, 2016 at 11:33

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