The question most enterprise buyers ask when choosing a VoIP provider for Microsoft Teams Phone is which one has the best rate card. It's the wrong question. Per-minute pricing differences between credible providers are small. The decisions that determine whether a Teams Phone deployment holds up under enterprise load sit elsewhere. They sit in the connectivity model, the geographic footprint, the coexistence path with existing infrastructure, and the network layer underneath the voice.
When choosing a VoIP provider for Microsoft Teams Phone, four criteria predict deployment success. Does the provider support both Operator Connect and Direct Routing? Can it cover your international footprint under a single contract? Will it coexist with the infrastructure you haven't retired yet? And does it own the network layer underneath the voice?
Microsoft Teams Phone integrates with VoIP providers through two Microsoft-certified models: Operator Connect and Direct Routing. Operator Connect is configured in the Teams Admin Center and suits organizations that want carrier-managed PSTN connectivity without owning SBCs. Direct Routing uses SIP trunking through Session Border Controllers. It suits enterprises with complex dial plans, legacy PBX still in service, or non-standard call routing requirements.
Enterprises with both straightforward sites and operationally complex ones often need both models running in parallel. A 12-site enterprise might run Operator Connect at nine corporate sites and Direct Routing at three sites with non-standard call flows. Both must come from the same provider, or the support model fragments. Ask any shortlisted provider whether they hold Microsoft certification for both, and whether they have customers running both simultaneously across the same tenant.
Microsoft Teams international calling fails most often in the gaps between regional carriers. A multinational deployment patched together from local carrier contracts splits billing across currencies and support across time zones. Accountability splits with it. Single-provider PSTN replacement removes that fragmentation.
Pure IP provides PSTN replacement in 50+ countries and SBC-based voice in 137, with billing in multiple currencies. A US-headquartered enterprise running Teams Phone across Europe, APAC, and Latin America can do so on one contract and one support path. Ask any shortlisted provider for their exact country list, not their marketing copy. Coverage either includes your operating footprint or it doesn't.
Most enterprises mid-migration still run legacy PBX, ATAs, paging systems, analog devices for door entry, and fax for compliance. The realistic migration timeline is three to five years, not one. A VoIP provider that requires a clean cutover to Teams Phone doesn't fit that timeline. It forces premature decommissioning of equipment that still has a job.
Pure IP connects across the stack: legacy PBX, cloud platforms, analog endpoints, contact center integrations. Modernization doesn't depend on retiring everything first. Ask the provider what their other customers have kept connected during migration, not what the platform technically supports.
Voice quality issues rarely originate in the voice layer. They originate in the WAN underneath: jitter, packet loss, asymmetric routing, congested last-mile circuits, misconfigured QoS. When voice and network sit with different providers, most quality incidents become triage exercises across two vendors pointing at each other.
A provider that runs both voice and network collapses that to one accountability path. Pure IP provides Managed SD-WAN and LTE/5G connectivity alongside voice infrastructure. One support team is responsible for the call from the application down to the underlay. The question to ask is who owns the call path end-to-end when something fails at 2am.
Four questions cut through most VoIP provider marketing on a Microsoft Teams Phone System evaluation call.
The answers separate providers built for enterprise Teams Phone deployments from those that resell connectivity and hope nothing breaks.
Pure IP runs enterprise Teams Phone voice across 137 countries on both Operator Connect and Direct Routing, with the network layer included. See how Pure IP supports Microsoft Teams enterprise voice, or get in touch to compare against your shortlist.