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Case study

CallHome

Affordable VoIP calling for the African diaspora.

A mobile calling app delivering real-time HD voice over a SIP/VoIP stack, engineered for the African diaspora and frequent travelers who were tired of expensive, unreliable international calling. Calls, international SMS, and mobile top-ups for Africa in one contract-free app.

  • VoIP
  • SIP
  • Kotlin
  • Swift
  • Android
  • iOS
  • Telecom
  • Mobile
CallHome VoIP app showing the dialer and low-cost call rates to African countries
CallHome top-up and international SMS screens with multiple payment methods
CallHome mobile call screen during an HD voice call to a contact in Africa
Results at a glance

Built for the realities of African mobile networks.

Stable HD on 3G+

The codec and signaling layer hold HD voice clarity on connections as slow as 3G, the most common real-world condition for diaspora calls.

Native on both platforms

Android in Kotlin and iOS in Swift, each built natively for first-class performance and deep system integration.

5 payment methods

Visa, Mastercard, PayPal, Mobile Money, and in-app purchase, so no user is excluded by their local financial infrastructure.

Every major African operator

Integrated mobile top-up covers all major operators across Africa, with no second app to juggle.

No contracts, no expiry

Fully prepaid and contract-free, and prepaid credit never expires, removing the pressure of time-limited top-ups.

Under 3 steps to first call

Sign up with a phone number, top up, and dial. No long forms or ID-verification delays before the first call.

The problem

Calling home had become expensive and unreliable.

For millions living outside Africa, staying connected with family and business contacts had become unnecessarily expensive and frustrating. Call rates to African countries were high, with hidden fees that only appeared at billing time. Quality was inconsistent, with frequent drops, echo, and lag even on a decent connection.

Most services required long-term contracts or complex registration that turned a simple need into a bureaucratic task. Mobile top-up for African operators was rarely integrated, forcing users to juggle multiple apps. And no single solution covered calls, SMS, and credit transfers for African destinations under one roof.

A Ghanaian family living in London wanted to call home daily. Every service they tried either charged heavily per minute, dropped calls mid-conversation, or made sending airtime to relatives a separate ordeal requiring an entirely different app.

CallHome call screen during an HD voice call between London and Accra
Technical architecture

SIP at the core, native on the edges.

CallHome's calling backbone uses the Session Initiation Protocol (SIP), chosen over proprietary alternatives for its reliability on constrained networks, its compatibility with carrier infrastructure across Africa, and the ability to fine-tune latency at the application layer.

The audio codec pipeline was optimized to sustain HD voice clarity on connections as slow as 3G, directly addressing the most common diaspora complaint, where caller and recipient are often on different network qualities at the same time.

The app was built natively: Kotlin for Android and Swift for iOS. Each platform got a purpose-built implementation to take full advantage of native APIs, platform performance optimizations, and deep integration with the system dialer, contacts, and audio stack.

The payment layer supports five distinct methods, a deliberate product decision to include users across different financial ecosystems, particularly markets where bank-card access is limited but Mobile Money penetration is high.

Stack
  • SIP / VoIP
  • HD audio codecs
  • Kotlin (Android)
  • Swift (iOS)
  • Native dialer & audio
  • Multi-gateway payments
  • Mobile Money

Cheap international calls to Africa with HD clarity

High-quality voice calls to any mobile or landline across African countries, with a codec pipeline tuned for clarity on low-bandwidth connections.

Instant international SMS

Send text messages internationally to any country directly from the app, without switching to a separate messaging service.

Mobile top-ups for all African operators

Transfer mobile credit to contacts across Africa covering every major operator, without ever leaving the application.

Smart contact management and call history

Intelligent sync with the user's existing contacts, combined with a full log of calls, messages, and top-up transactions.

Transparent pricing

Rates are shown clearly before dialing, with no additional charges introduced at billing time and no expiry on prepaid credit.

Native on Android and iOS

Available on both platforms, built natively on each for optimal performance and a first-class feel in the system dialer.

Engineering decisions

Three calls that shaped the build.

01

Choosing SIP over proprietary VoIP

Proprietary stacks promise convenience but degrade unpredictably on weak networks. SIP was selected for its reliability on constrained connections, carrier compatibility across Africa, and the ability to tune latency at the application layer, which is exactly where diaspora calls live.

02

Holding HD voice on asymmetric networks

The hardest real-world case is a caller on 4G in London and a recipient on 3G in Accra at the same time. The codec and signaling pipeline were optimized to keep clarity and minimize drops across that asymmetry, not just in lab conditions.

03

Five payment rails into one balance

Card-first payment design excludes large parts of the target market. Integrating Mobile Money alongside Visa, Mastercard, PayPal, and in-app purchase meant no user is locked out by the financial infrastructure of where they happen to live.

Who CallHome is built for

One product, designed around a specific community.

The African diaspora

People in Europe, North America, or the Middle East calling family in West and Central Africa regularly, who prioritize call quality, low per-minute rates, and sending airtime to relatives who may not have the app.

Frequent travelers

Professionals and travelers moving between countries who need a stable, roaming-independent calling solution that does not depend on local SIM cards or expensive roaming tariffs.

Distributed families and businesses

Families and organizations operating across multiple countries who need a cost-predictable, reliable channel managed from a single account with transparent billing.

Outcome

CallHome shows how a product designed around a specific underserved community, with infrastructure decisions made explicitly for that community's network reality, can outperform general-purpose alternatives. Rather than adapting a Western calling product for an African audience, CallHome was built in reverse: starting from the constraints of African mobile networks and working outward. The result is an app where a grandmother in Accra receives a call from her daughter in London with the same clarity they would expect from a local call, at a price that does not make either of them think twice before dialing.

This team is the best with whom I've worked.

ETechViral has delivered a user-friendly app that meets the client's needs. The team showcased excellent project management, delivered quality work on time, and respected the project's deadlines throughout the engagement, communicating via virtual meetings, emails, and messages.

ExecutiveCallHome Monde
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