Can't call out of VN? Need help quick

I wonder whether your Irish service provider has put a block on the roaming feature since it should be any problem at all.
Mine does have several blocking options: not roaming, not data traffic on roaming,.. Normally, those options are not default, but it seems like they are active in your case.

Best to contact them and ask.

Ah ok, I wasn't sure if it was a problem with them or with Viettel. Cheers!

also, it is quite common for those service providers to let you log in their website so that you can activate/deactivate those options yourself on your subscriptions. It would save you both time and cost to call them.

There are high incidents of long distance/overseas fraud emanating from VietNam, as well as credit card fraud.

Slowly systems are being put in place to combat this and, equally slowly, CC usage is being opened up.

If you use a CC in a shop or restaurant do not let it out of your sight, follow it if need be. Trustworthy restaurants are increasingly using portable, encrypted WiFi, terminals to ease your mind.

Concerning credit card, terminal system in Vietnam is actually better equipped that many countries (including the US).

While other countries still use the easy-to-copy magnetic strip, many terminals in Vietnam use the smartcard system which requires pin code identification.

In addition, card issuers in many countries now allow selective blocking. Mine, for example, allows me to select whether I can use the card in each of the following regions: Asia, Europe, US,... I can at any time go online to activate/deactivate any of the regions.

Buzzer, I know with my uk sim if I use that to dial the uk, what happens is I get a automated call back and then have to dial out through that gateway.
Tbh it's a pain in the but, far easier to get a local sim and dial out using that and much cheaper too