How Belfius added borderless mobile data to their banking app

In June 2025, Belfius became the first Belgian bank to offer borderless mobile connectivity inside their banking app. Belfius customers can now use their banking app abroad without roaming charges or extra data plans, powered by Firsty's eSIM infrastructure.

This case study covers what they built, how it went live, and what we learned about embedding connectivity into a financial product.

The problem

Belfius's customers travel. Their banking app is their primary tool for managing money: balances, transfers, card controls, fraud alerts. When customers travel abroad, several things happen:

1. International roaming costs deter them from using mobile data
2. Public WiFi raises security concerns for banking
3. Customers buy local SIM cards, but those don't keep their primary number
4. Two-factor authentication SMS messages depend on the customer being reachable

The combined effect: a banking app that's most needed when traveling is least used. Belfius wanted to fix this.

The solution

Inside the Belfius app, customers can activate a free Firsty eSIM. It provides low-bandwidth data (enough to use the banking app) in 160+ countries with no roaming charges, no setup, and no extra cost to the customer.

Higher bandwidth plans (for video calls, streaming, normal browsing) are available as optional upgrades, but the core banking-app-only tier is free for all Belfius customers.

From the customer's perspective:

1. Open Belfius app
2. Tap "Activate worldwide connection"
3. Verify their identity (one tap, already authenticated in the app)
4. eSIM installs automatically on supported devices
5. Done

From Belfius's perspective:

1. Customer eligibility check via Belfius's existing customer database
2. Firsty API call to provision the eSIM
3. Activation code delivered to the app
4. Native eSIM installation via iOS/Android entitlements

The whole flow takes 30 seconds for the customer.

Architecture

Belfius integrated Firsty as a backend service. The Belfius app talks to Belfius's backend; Belfius's backend talks to Firsty's API. The customer never sees Firsty branding (white-label arrangement).

Key components:

Eligibility service: checks if a customer qualifies for the free tier. Adult, in good standing, has an eSIM-compatible device. Belfius's existing identity infrastructure handled this.

Provisioning service: calls Firsty's two-step API. Creates an eSIM profile, attaches the appropriate plan based on customer tier. Returns the activation code to the app.

Activation UX: the Belfius app uses iOS's CTCellularPlanProvisioning and Android's eUICC entitlements to install the eSIM in-app, without requiring the customer to scan a QR code.

The native in-app provisioning is the magic. Most travel eSIM apps require QR code scanning. Belfius leveraged carrier-app entitlements (which they obtained as a regulated financial institution) to install the eSIM with a single tap.

Timeline

The full project from "let's explore this" to "shipped in production" was just under six months. Breakdown:

• Month 1: technical evaluation, contract negotiation
• Months 2-3: API integration, eligibility logic, internal testing
• Month 4: iOS/Android entitlement applications (Apple's process is slow)
• Month 5: customer testing with Belfius employees
• Month 6: public launch

The hardest parts weren't technical. They were:

1. Getting Apple to approve in-app eSIM provisioning entitlements
2. Reviewing the customer data flow for GDPR compliance
3. Designing the eligibility logic for the free tier

The actual API integration with Firsty took about three weeks of one engineer's time.

What worked

Two-step provisioning made the activation flow flexible. Belfius could create profiles in advance for high-traffic periods (summer travel) without committing to specific plans until customers activated.

Multi-IMSI failover prevented outages. During a regional outage in southern Europe in August 2025, Belfius's customers stayed connected because the SIMs silently switched to backup carriers. Belfius's product team didn't even hear about the outage until they read Firsty's incident report.

The "free for banking" tier created a viral moment. Customers showed each other the feature. Word-of-mouth growth was significant; Belfius's PR around launch reached media well beyond financial press.

What we learned

Bank app integrations require more compliance work than technical work. The API integration is straightforward. The data flow review, security audit, and contractual paperwork took longer than writing code.

Native in-app eSIM provisioning beats QR codes for embedded use cases. If you have carrier app entitlements (which any regulated entity can apply for), the customer experience is dramatically better.

Free connectivity is a strong customer loyalty signal. Belfius's customer satisfaction scores around international travel improved measurably in the first three months after launch.

What's next for Belfius

Belfius continues to expand the Firsty integration:

• Adding higher-tier plans for premium customers
• Exploring connectivity for business banking customers
• Integration with their travel insurance product

Could this work for your bank or fintech?

If you're a regulated financial institution thinking about adding connectivity, the Belfius pattern works. The requirements:

• Existing identity infrastructure (KYC, authentication)
• Ability to apply for iOS/Android carrier app entitlements
• A reason for customers to value the feature (international travel use cases work best)

The technical integration is the easy part. Firsty's API gives you provisioning. Your job is the customer experience and the business logic for who gets what tier.

If you're considering this, contact us for a conversation. We can walk you through how Belfius did it and what we'd recommend for your context.