How to set up roaming on eSIM or physical SIM card in Nha Trang Vietnam?

In August 2026 a traveler who bought an eSIM on Trip.com said mobile data worked on it but regular calls did not; she never found out why and made calls through messenger apps instead.

Calls over an eSIM: in late July 2026 a participant clarified that using the eSIM in place of Wi-Fi for calls did not work for her — calls needed an actual Wi-Fi connection, and even Wi-Fi shared from another phone was enough.

How to keep receiving bank SMS on your home number while using an eSIM for data: in July 2026 a participant described that on Android both SIMs stay active — data and roaming are on for the eSIM, while on the home SIM mobile data is off but the SIM itself stays on, so SMS and calls still arrive. Her friend's iPhone had no physical slot and only one eSIM could be active at a time, so she had to switch: turn off the international eSIM, turn on the home one to receive SMS, then switch back to the international eSIM and mobile data.

According to another traveler in July 2026, her eSIM configured itself and she did not need to enable roaming manually: after installation you select that eSIM under Cellular settings, and on arrival mobile data works on it automatically. In August 2026 another traveler said that after arriving in Vietnam he started a Viettel eSIM, received an SMS on his home SIM and changed nothing else — everything worked automatically.

In June 2026 a traveler wrote that she had to turn on roaming on the eSIM, while her regular SIM card simply stayed in the phone and all SMS kept arriving. Another participant added in late June that the roaming switch is in the provider's personal account and requires sending an SMS; they no longer remembered the exact command, so check it with your eSIM provider.

Based on several travelers' experience in summer 2026, a regular physical SIM card can stay in the phone without any extra setup: SMS keep arriving on the home number. One traveler warned that it is better not to answer incoming calls on the home number while roaming, as that gets expensive. A participant with a US T-Mobile number confirmed in July 2026 that messages were still arriving on it.