• Vietnam has switched off its remaining 2G networks outside designated island and offshore areas from 15 September
  • Some older 4G phones may retain mobile data but lose voice calls if VoLTE is unsupported or not enabled

The fact

Vietnamese mobile operators ended ordinary 2G GSM service from 16 September, completing the second stage of a phase-out that began in 2024. The network had been permitted to operate through 15 September, with exceptions for service in the Truong Sa and Hoang Sa archipelagos and on DK offshore platforms. The first phase stopped service to 2G-only handsets while keeping GSM available during the transition. The shutdown frees spectrum, including frequencies in the 900MHz and 1800MHz bands, for newer mobile networks.

The remaining device problem is not limited to 2G phones. Some early 4G handsets use LTE for data but fall back to an older network for voice calls. Voice over LTE, or VoLTE, keeps those calls on 4G instead. Vietnam's Ministry of Science and Technology said 4G coverage now exceeds 99% of the population and operators have upgraded their VoLTE systems, but warned that 4G and 5G phones without VoLTE support or activation may still lose voice service after the shutdown. MobiFone has separately told 4G customers to check compatibility, register for VoLTE and enable it on their phones.

The assessment

Businesses can have a phone that looks ready for 4G and still find that calling no longer works. A device may show a 4G data connection while its voice service was quietly falling back to 2G. That makes an asset list based only on handset generation unreliable. Not every affected phone needs replacing. Some compatible devices may only need VoLTE turned on or a newer SIM, while others do not support the service at all. Testing the actual handset and subscription first can separate a settings problem from a hardware problem and avoid unnecessary replacements.

For BTW readers, a working data connection is no longer enough to show that a business phone survived the transition. Teams need to confirm that staff can still make and receive calls on 4G. That check will quickly show which devices need a setting or SIM change and which genuinely need replacing.

What to watch

Watch operator notices and support cases after the shutdown, especially for older 4G models. Failed calls should be traced to handset compatibility, SIM support or VoLTE activation rather than treated as one problem. Coverage complaints will also show where newer networks still need work after 2G disappears.