You’ve probably lost count of how many mobile devices your organization manages today, and they’re all part of a growing web of Subscriber Identity Modules (SIMs) connecting your workforce to everything they do. A few years ago, it was simple: one employee, one device, one SIM. Now? Research from IDC shows that 2-3 devices per worker is typical, and many of those devices carry multiple SIMs of their own. In 2024, more than half of all devices shipped supported eSIM technology.
That flexibility is powerful, but it also blurs the edges of control. Every new SIM represents another identity to secure, another endpoint to trust, and another potential point of risk. IDC’s data backs it up: SIM-swapping is now the top mobile security incident reported by IT leaders.
Multi-SIM environments also add complexity to inventory management. Devices may have multiple active lines, and lines may span multiple devices. IT and finance leaders need to accurately map and display these relationships, so inventory is always current, connected, and clearly represented. Without that visibility, it’s nearly impossible to manage costs, track usage, or enforce policies consistently.
For these reasons, organizations need to start thinking about SIM management as seriously as device management – moving away from outdated, manual approaches toward greater visibility, automation, and control. In response, more are investing in Managed Mobility Services (MMS) platforms that can manage and secure all devices and expenses in real-time with advanced analytics. The right MMS platform will be sophisticated enough to handle lifecycle control, expense management, security intelligence, and inventory management for devices that are part of a one-to-many relationships (one device, multiple lines; one line, multiple devices).
Keep reading to explore the growth of multi-SIM environments, how risk creeps in, and how MMS closes the gaps.
SIMs: A Quick Explainer
A SIM (or SIM card) is what allows a device to identify itself on a mobile network. It’s like the device’s digital passport, storing the phone number, carrier information, and unique identifiers that authenticate the connection.
Traditionally, SIMs were small, removable chips you could pop in and out of devices. Today, many are digitally embedded – known as eSIMs. You don’t have to insert a chip because it’s built onto the device’s mainboard. In this way, new SIM profiles can be downloaded directly onto the device in just a few taps.
There are also integrated SIMs, or iSIMs, which take this a step further. They offer the same functionality as an eSIM but are built directly into the device’s main processor. No separate chip is required because the capability is fully integrated. eSIMs and iSIMs both fall under the category of “digital SIM.”
With digital SIMs, one phone can host multiple profiles at once: a corporate line, a personal number, even a temporary travel plan. Users can switch between them in their device’s settings and customize which SIM handles which function. One SIM might handle work calls, another personal communication, and a third data while traveling. Multiple lines can stay active – all you need to do is set your defaults and toggle as needed.
Multiple devices can also support one SIM. A common real-world example is the traveling executive who carries both a smartphone and a tablet. They need connectivity on both devices but want to use the same phone number between them. Multi-SIM makes that possible, allowing a single number or data plan to extend to multiple devices.
In short, SIMs have evolved from simple plastic cards into a digital ID that drives productivity and enriches the employee experience.
What’s driving the use of multiple SIMs?
Part of the shift stems from how work itself has evolved. Hybrid models and bring-your-own-device (BYOD) policies have blurred the line between personal and professional life – something multiple SIMs cleanly separate. Employees can use one SIM strictly for corporate calls and data, and IT teams get visibility into just that SIM without encroaching on personal use.
There are also practical reasons like cost and coverage. Traveling employees can load a local eSIM instead of paying roaming fees. In Europe, where crossing borders is like crossing state lines, picking up a SIM at the airport is second nature. In the U.S., field teams use dual-SIM devices to maintain coverage across multiple carriers with the phone automatically connecting to the strongest signal.
And then there’s the reverse scenario of one SIM, multiple devices – like in the example above with the traveling executive who might use both a smartphone and a tablet under the same number or plan to stay connected on-the-go.
Why are SIM-related attacks growing?
Let’s focus on the fastest growing SIM-related attack: SIM-swapping, as reported by IDC.
This is when attackers try to convince a carrier to transfer a victim’s phone number to a new SIM that they control, most often by impersonating the victim or exploiting weak carrier authentication. Once the number is moved, the attacker can receive the victim’s calls and texts, intercept one-time passcodes or two-factor authentication, and reset passwords to take over accounts. The goal is almost always to gain control of a corporate number that’s tied to sensitive systems.
Attackers also go after users themselves, using phishing (e.g., fake carrier or IT emails that steal login credentials), smishing (e.g., text messages with malicious links or fake security alerts), and deceptive eSIM prompts (e.g., fraudulent QR codes or “travel SIM” offers that install attacker-controlled profiles) to bypass corporate defenses from the inside.
A study of five major U.S. prepaid carriers found that 80% of first-attempt SIM-swap frauds were successful. That’s a high success rate, and the potential for monetary gain is also high. In 2023, the FBI investigated more than 1,000 SIM-swap attacks and totaled nearly $50M in reported losses.
In a nutshell: more SIMs to manage + weak carrier authentication = a growing blind spot attackers are eager to exploit.
Why do I need a dedicated strategy for multi-SIM management?
Let’s start by defining what a “dedicated” multi-SIM management strategy means.
What it Is
An intentional framework for how SIMs are managed end-to-end. This includes central visibility into every active SIM, user, and device; automated provisioning and deactivation to eliminate manual errors; policy enforcement that governs how and where SIMs are used; and cost and security alignment so usage, spend, and risk are all tracked in one place.
It should also include comprehensive reporting to account for regional billing differences. In the U.S., multi-SIM plans often share one primary line with add-on fees for extra devices. In Europe and the U.K., each SIM typically functions as its own line under a shared account – requiring a different inventory management approach. The right MMS platform will be able to handle either scenario with ease.
Another thing to consider is Mobile Threat Defense (MTD). As employees download apps, click links, and browse sites, MTD acts as a watchdog for every device. It monitors activity, flags risky behavior, and intervenes at the device level – a crucial defense layer for those phishing, smishing, and deceptive eSIM prompts that attackers attempt.
What it Isn’t
A spreadsheet of phone numbers, carrier plans, and expiration dates, sporadic inventory checks, or relying on employees to manage their own eSIMs when traveling. As the number of devices, SIMs, and carriers grows, it’s virtually impossible for IT teams managing mobility manually to tell which SIMs are active, who they’re assigned to, or whether they comply with security policies.
How does MMS streamline and improve multi-SIM management?
A modern MMS platform like Tangoe One Mobile brings centralized visibility and control to the entire mobile ecosystem – devices, SIMs, carriers, and costs – under one pane of glass. Instead of dealing with disconnected spreadsheets and carrier portals, IT and finance leaders can see every active line, every profile, and every user in real-time.
This changes the game:
- End-to-end lifecycle management. From activation to cancellation, Tangoe One Mobile automates the full lifecycle of each device – provisioning, suspending, reallocating, or retiring lines as employees join, change roles, or leave the organization – including multi–SIM devices.
- Real-time insight and governance. Direct carrier integrations pull real-time information on active lines, SIM identifiers, usage, and billing into one centralized view, so you can see every line across carriers and regions in a single dashboard. You’ll instantly clarify the complexities of different billing structures with reports that normalize those variations, delivering one consistent view of spend and usage.
- Data normalization and global intelligence. Tangoe One Mobile standardizes carrier data across formats and currencies, giving global organizations a single source of truth for spend, utilization, and ownership. That unified dataset makes it easy to do apples-to-apples cost comparisons and identify savings opportunities across carriers, countries, and contracts.
- Built-in MTD. We integrate with MTD so you can start detecting and containing threats at the device level – whether it’s risky apps, phishing attempts, or malicious network activity.
- Consulting and advisory services. Tap into 60+ technology experts for insider intelligence to help save money, implement new technologies, and support key IT initiatives.
More SIMs, more risk? Not with the right tools, strategy, and support. See how Tangoe’s MMS platform clarifies and controls multi-SIM mobile environments.