If you’re evaluating your business phone system in 2025, you’ve almost certainly asked the same question thousands of other IT decision-makers are asking: should we just use Teams Calling, or do we need a dedicated hosted VoIP solution?
On the surface, Teams Calling looks like a no-brainer. You’re already paying for Microsoft 365. Teams is open on every laptop. Folding calls in feels like the path of least resistance.
But reliability, cost, and control tell a different story, and for businesses where the phone is a critical channel, the wrong choice has real consequences.
This blog post is an honest, category-by-category comparison.
1. Uptime and Reliability
Teams Calling
Microsoft publishes a 99.9% SLA for Microsoft 365, which sounds solid until you look at what it actually covers. That SLA applies to the entire platform. Teams Calling is not a standalone service; it’s a feature inside Microsoft 365, which means it shares its fate with everything else in that ecosystem.
When Microsoft 365 suffers an outage, whether the root cause is a coding error, a DNS misconfiguration, or an authentication failure, your phone system goes down alongside your email, calendar, and chat. In March 2025, Microsoft investigated a significant outage in which users couldn’t receive calls via Teams-provisioned auto-attendants and call queues. In October 2024, a separate incident caused call queue calls to return “Line Busy” errors across multiple organisations. Both incidents were caused by underlying platform issues, not voice-specific failures.
Hosted VoIP
A purpose-built hosted VoIP solution runs on infrastructure dedicated entirely to voice. At Fuse 2, our network is built on Oracle’s enterprise-grade infrastructure, virtualised across geographically diverse data centres. We contractually guarantee 99.95% uptime specifically for VoIP services, and because voice runs on its own infrastructure, an outage in your email or productivity stack has zero impact on your calls.
Hosted VoIP wins.
The margin isn’t just in the numbers, it’s architectural. Independent voice infrastructure eliminates an entire category of failure risk.
2. Failure Independence
For any business running an inbound call function, this is the category that matters most.
Teams Calling
Since Teams Calling depends on Microsoft 365 authentication, DNS resolution, and a stack of interconnected cloud services, a failure in any one of those layers can silence your phones!
Microsoft’s own post-incident reports have documented call failures caused by authentication system coding errors and Entra ID authentication failures, neither of which has anything to do with voice directly. Your customers still can’t get through.
Hosted VoIP
Voice traffic is completely separated from productivity applications. Your phones are on a different network, managed by a different provider, running on different infrastructure. If Microsoft goes down, your calls keep routing. If your internet connection degrades, failover can redirect calls to mobile or another site. The two systems simply don’t share failure modes.
Hosted VoIP wins
This is the single biggest structural difference between the two approaches.
3. Call Quality
Teams Calling
Call quality in Teams is affected by multiple variables: your Microsoft 365 tenant configuration, your internal network, the SBC sitting between your network and Microsoft’s cloud (in a Direct Routing setup), and Microsoft’s own routing decisions. When quality is poor, diagnosing the root cause is genuinely difficult. Microsoft’s Call Quality Dashboard provides some visibility, but interpreting it meaningfully requires significant expertise, and many of the contributing factors sit outside your environment entirely.
Hosted VoIP
A dedicated voice network is optimised for one thing: delivering high-quality calls. Fuse 2’s intelligent session routing engine evaluates quality metrics in real-time and selects the best route for each call leg. There are:
- No competing workloads on the network
- No shared authentication layers
- No intermediary platform introducing latency or jitter between your users and the PSTN.
Hosted VoIP wins.
Fewer variables, better routing, and a network built exclusively for voice deliver consistently higher quality.
4. Diagnostic Visibility
Teams Calling
When something goes wrong with a call, the standard tools available to most SMBs are limited. The Teams Admin Centre and Call Quality Dashboard offer some data, but they require specialist knowledge to interpret, and a significant portion of call quality issues are caused by factors entirely outside your control or visibility. Escalating to Microsoft is rarely a fast or satisfying experience.
Hosted VoIP
With Fuse 2’s Orca Portal, your team has direct, real-time visibility into your voice network. Usage analytics, live performance metrics, and automated provisioning are all available through a single dashboard, and with our new premium upgrade, ORCA+, you’ll have access to advanced call detail analytics, giving you a granular, end-to-end view of every call. When a fault occurs, you’re escalating to engineers who own and operate the infrastructure, not navigating a support ticket queue into a hyperscaler.
Hosted VoIP wins.
Owning the diagnostic layer means faster resolution and clearer accountability.
5. Cost and Licensing
Teams Calling
The “it’s already included” assumption breaks down quickly when you look at the actual licence structure. To make and receive external calls via Teams, you need:
- A Microsoft 365 licence (Business Basic starts at £4.90/user/month at current pricing)
- A Teams Phone add-on licence
- Either a Microsoft Calling Plan (with limited included minutes and per-minute charges beyond that) or a Direct Routing setup with a compatible SBC
International calls are typically charged separately. For organisations with meaningful call volumes or international requirements, these costs accumulate quickly. And because you’re inside Microsoft’s licensing model, price changes or feature reclassifications are outside your control.
Hosted VoIP
SIP trunks are shared across your organisation rather than allocated per-user, which means the cost model scales more favourably as headcount grows. Combining a 3CX licence with Fuse 2 SIP trunks typically delivers a lower per-seat cost than an equivalent Teams Calling configuration, with more features included as standard.
Hosted VoIP wins
Particularly at scale, the further you are from a handful of light users, the more the economics favour a dedicated solution.
6. Feature Depth
Teams Calling
Core telephony features are available: call queues, auto attendants, voicemail, and basic call recording. For many businesses, this is sufficient. However, advanced features often require additional licences, and the feature set is ultimately constrained by what Microsoft chooses to include in its calling product.
Hosted VoIP
A hosted VoIP platform built around 3CX and carrier-grade SIP trunks delivers a comprehensive feature set as standard: call recording, voicemail-to-email, number masking, intelligent call forwarding, real-time analytics, IVR, ring groups, and CRM integrations. This way, you’re not waiting for Microsoft to add something to its roadmap or paying extra to unlock functionality that should be table stakes.
Hosted VoIP wins.
More features, fewer add-on licences, more control over configuration.
7. Administration and Number Management
Teams Calling
The Teams Admin Centre is functional, but number porting through Microsoft is notoriously slow and administratively burdensome. Adding users, managing call flows, and making configuration changes requires navigating Microsoft’s admin layer, which, for non-specialists, can be time-consuming and opaque.
Hosted VoIP
Fuse 2’s Orca Portal is purpose-built for fast, self-service number and system management. You can purchase SIP trunks, DIDs, and 3CX licences instantly, initiate number ports across 240+ locations, and manage provisioning from a single interface. Configuration changes that take days with Microsoft can take minutes with a dedicated provider.
Hosted VoIP wins.
Self-service portals built for voice give you speed and clarity that platform-embedded admin tools simply don’t match.
8. Microsoft 365 Integration
This is where Teams Calling earns its keep, and it’s worth being honest about.
Teams Calling
If your team lives in Microsoft Teams, using it for chat, meetings, file sharing, and project collaboration, having calls natively integrated is genuinely useful. Presence, call history, voicemail, and meetings all live in one place. For organisations where internal calls vastly outnumber external ones, this workflow integration is a real advantage.
Hosted VoIP
VoIP platforms can integrate with CRM systems, helpdesks, and other business tools, but they don’t offer the same native Teams experience. If deep Microsoft 365 integration is a priority, this is a genuine trade-off.
Teams Calling wins.
If your business is heavily Microsoft-centric and internal communication is the primary use case, this matters.
The Scorecard
| Category | Teams Calling | Hosted VoIP | Winner |
| Uptime SLA | 99.9% (platform) | 99.95% (voice-dedicated) | Hosted VoIP |
| Failure independence | ✗ Shared with M365 | ✓ Fully independent | Hosted VoIP |
| Redundancy & failover | Microsoft-controlled | Provider-controlled, real-time | Hosted VoIP |
| Voice quality | Variable | Optimised, dedicated | Hosted VoIP |
| Diagnostic visibility | Limited | Full portal access | Hosted VoIP |
| Cost at scale | High (per-user licences) | Lower (shared trunks) | Hosted VoIP |
| Feature depth | Core features | Comprehensive, included | Hosted VoIP |
| Administration | Slow, complex | Fast, self-service | Hosted VoIP |
| M365 / Teams integration | Native | Third-party | Teams Calling |
Who Should Choose What
Teams Calling is a reasonable fit if:
- Your team is deeply embedded in Microsoft 365
- The majority of your calls are internal
- Call volume is low, and inbound calls are not business-critical
- Workflow integration with Teams is more important than carrier-grade reliability
Hosted VoIP is the right choice if:
- Inbound calls are a primary customer touchpoint
- You run a reception, support desk, or any inbound call function
- Missed calls have a direct business cost
- You need transparent pricing that doesn’t compound with headcount
- You want accountability from a provider who owns the infrastructure
A Note on the Architecture
The fundamental difference between these two approaches isn’t about features; it’s about what sits underneath them.
Teams Calling is voice as a by-product of a productivity platform. Hosted VoIP is a voice as a product. When something goes wrong with a productivity platform, voice goes with it. When something is wrong with your dedicated voice infrastructure, you have a provider with an NOC, an SLA, and engineers whose only job is to fix it.
For any business where the phone matters, that distinction is worth more than the convenience of a single interface.
How Fuse 2 Can Help
We at Fuse 2 are an independent cloud communications provider operating our own global carrier-grade network. We specialise in hosted VoIP, SIP trunks, 3CX deployments, and direct routing solutions for businesses of all sizes, from SMBs to multi-site enterprises.
If you’re questioning whether your current voice setup is doing enough, or if you’d like a direct comparison against your current Teams Calling costs, we’re happy to walk you through it.
Speak to the Fuse 2 team →
