If you are travelling to Vietnam, you will now be able to enjoy free incoming and outgoing voice calls to Singapore by dialing the number directly. Likewise, if your SIMBA plan comes with free IDD mininutes, you can also call direct from the dial pad by dialing +IDDcountrycode followed by the number of the destination.
In order to do that, if you are not roaming on MobiFone, go to settings->mobile network->select SIM1 or 2 -> mobile networks -> Uncheck automatic select network. Click Next and it will prompt yuou to choose network manually. It will scan for all the networks available. Select MobiFone as the Roaming partner.
If everything works out (take note that the partner might not have enabled the feature depending on location), you should see a VoLTE logo on your status bar.
Now, you can call back Singapore directly by calling +65 followed by local mobile or fixed line number.
