The milestone reflects strong customer adoption and represents the fastest growth recorded by an OTT application in Viet Nam.

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A staff member guiding an user on how to install the Viettel Tammi app

Unlike Viettel’s previous standalone apps, Tammi serves as a super-app layer, integrating nearly 50 services into a single interface powered by an intelligent AI agent. Since its internal testing and launch, users have rated its calling, chat, and meeting functions highest among the five core features initially introduced.

Tammi addresses common limitations of internet calling, particularly declining call quality when connections are unstable. Unlike OTT platforms that operate separately from telecommunications infrastructure, Tammi combines its OTT service layer with Viettel’s domestic network and uses core technologies developed and mastered by Viettel to optimize processing speeds, an important factor in ensuring the quality of free calls.

One of Tammi’s distinctive features is cross-app calling through App-to-Phone and Phone-to-App connectivity, allowing Tammi users to call regular phone numbers even if the recipients have not installed the app, and vice versa. The feature extends OTT communications beyond communities using the same application and supports users in situations such as weak cellular signals when Wi-Fi remains available or disrupted roaming connections.

Another notable feature is online meetings. Tammi supports group video calls with up to 100 participants simultaneously and offers free meetings of up to 120 minutes, two to three times longer than the typical 40- to 60-minute limit of other online meeting applications, meeting a wide range of needs, from classrooms to corporate conferences. 

The 5-million-user milestone marks an initial step in Viettel’s effort to develop Tammi into a Vietnamese-built platform for communication and digital life, with calling and chatting serving as core functions for building users’ daily habits.

Translated by Tran Hoai