As IoT deployments expand across borders and industries, many organisations turn to global IoT SIM cards to simplify connectivity. On paper, a global SIM sounds ideal: one SIM, one APN, one contract, and coverage in dozens of countries.

But the reality is more complex and understanding how global IoT SIMs actually behave is essential for building reliable IoT solutions.

What Is a Global IoT SIM Card?

A global IoT SIM card is a SIM profile designed to work across multiple countries using roaming agreements. Instead of being tied to a single domestic operator, it can connect to partner networks around the world.

In theory, this means:

• One SIM works globally
• No need to swap SIMs when crossing borders
• Centralised billing
• Consistent APN and security policies

But behind the scenes, global SIMs still behave like roaming SIMs and that comes with limitations.

How Global IoT SIMs Actually Work

Every global IoT SIM has a home network, even if it’s marketed as “global”. This home network is usually based in the EU or US.

When the device powers on, the SIM follows a strict priority order:

1. Connect to the home network
2. If the home network is unavailable, connect to a roaming partner
3. Stay on that network until it becomes completely unusable

This behaviour is built into the SIM profile and is part of how roaming works worldwide.

The Hidden Problem: Home Network Preference

Here’s the issue most businesses never hear about:

A global IoT SIM will always try to use its home network even if the signal is extremely weak or unable to pass data.

This means:

• Devices cling to a poor‑quality network
• They ignore stronger networks nearby
• They appear “connected” but cannot send or receive data
• They repeatedly attempt to attach to the home network, draining power and causing downtime

This is a major problem in rural areas, indoor environments, moving vehicles, and countries where the home operator has limited coverage.

Why Does This Happen? Commercial Reasons, Not Technical Ones

Major operators such as Vodafone, Telefónica, Orange, and others offer global IoT SIMs that behave this way because it benefits their commercial agreements, not because it benefits the customer.

These operators:

• Want devices to stay on their own network whenever possible
• Prioritise roaming partners that offer the best wholesale rates
• Steer devices away from networks that cost them more
• Lock SIMs into preferred network lists

This is known as network steering, and it is driven entirely by commercial incentives, not by performance, reliability, or customer needs.

In other words:

Global SIMs are designed to protect the operator’s revenue, not your uptime.

The Impact on IoT Deployments

This behaviour can cause:

1. Unreliable Connectivity

Devices appear online but cannot pass data.

2. Higher Latency

Traffic may be routed back to the home country.

3. Increased Power Consumption

Devices constantly search for the home network.

4. Poor Performance in Critical Applications

CCTV, EV chargers, telematics, and industrial systems all suffer.

5. Difficult Troubleshooting

The device “looks connected” but behaves unpredictably.

Why Many Businesses Are Moving to Unsteered Multi‑Network IoT SIMs

To avoid these issues, many organisations now choose unsteered multi‑network IoT SIMs instead of traditional global SIMs.

Unsteered SIMs:

• Do not prioritise a home network
• Allow the device to choose the strongest available operator
• Avoid ghost‑signal problems
• Deliver lower latency
• Improve uptime and stability
• Work better with intelligent routers (Teltonika, Robustel, Cradlepoint, Ericsson, etc.)

This gives the device true freedom to attach to the best network — not the one the SIM is commercially steered toward.

Conclusion: Global SIMs Are Convenient — But Not Always Reliable

Global IoT SIM cards offer simplicity, but they come with a built‑in limitation:

They always prefer their home network, even when it’s the worst option available and major operators like Vodafone and Telefónica design them this way for commercial reasons.

For IoT deployments where uptime, stability, and performance matter, unsteered multi‑network connectivity is often the smarter choice.

It ensures devices stay online, choose the best network, and avoid the pitfalls of home‑network steering & delivering the reliability modern IoT applications demand.