Microsoft Teams Phone Guide for Government: GCC vs GCC High

Microsoft Teams is popular with many government agencies and contractors. Chat, meetings, and file sharing are familiar, widely adopted, and relatively straightforward to deploy. While adding Teams Phone to the setup feels like a natural next step, in government environments, it’s not so straightforward. 

As soon as Teams is used for PSTN calling, it stops being just a collaboration tool and becomes part of your organization’s regulated communications infrastructure. Voice brings new considerations around data handling, access controls, call metadata, and regulatory scope. And those considerations are tightly bound to which Microsoft government cloud you’re operating in.

Both GCC and GCC High are designed to support government workloads, but they exist for very different compliance boundaries. Choosing the wrong environment for Teams Phone can introduce compliance exposure that’s difficult, expensive, and disruptive to correct after deployment.

In this article, we’ll explain how Microsoft Teams Phone for Government works, break down the real differences between GCC and GCC High, and show why compliance requirements should drive this decision from the outset.

Overview: Microsoft GCC vs GCC High

Microsoft offers two government-specific cloud environments to support public-sector workloads: GCC and GCC High. While they share some similarities, they are designed for different regulatory thresholds and risk profiles. Understanding this distinction at a high level is essential before looking at how Teams Phone and PSTN calling behave in each environment.

Microsoft Government Community Cloud (GCC)

Microsoft Government Community Cloud (GCC) is designed for U.S. government agencies and contractors that need a government-aligned cloud environment but are not subject to export-control or national security regulations.

GCC operates within Microsoft’s government cloud framework and supports compliance standards commonly required by federal, state, and local agencies, including FedRAMP Moderate. Data residency and access controls are aligned with U.S. government requirements, but GCC does not enforce the same isolation or personnel restrictions as GCC High.

Typical GCC use cases include civilian federal agencies, state and local governments, and contractors working on non-defense or non-export-controlled programs. For many organizations, GCC provides a compliant and cost-effective environment for collaboration and productivity without the added complexity of national-security-level controls.

Microsoft Government Community Cloud High (GCC High)

Microsoft Government Community Cloud High (GCC High) is built for the most highly regulated government and defense workloads. It exists specifically to support organizations that must comply with FedRAMP High, ITAR, DFARS, and other export-control or defense-related requirements.

GCC High runs on Azure Government, which is physically and logically isolated from Microsoft’s commercial cloud. It enforces U.S.-only data residency, restricts access to U.S.-citizen, screened Microsoft personnel, and applies tighter controls around identity, access, and service operations.

GCC High exists alongside GCC because not all government workloads carry the same regulatory burden. For defense contractors, DIB organizations, and agencies handling controlled unclassified information (CUI) tied to national security or export controls, GCC High provides the level of isolation and assurance that GCC is not designed to offer.

Teams Phone in GCC vs GCC High: Key Differences

The differences between GCC and GCC High become clear when Teams is used for PSTN calling. Compliance alignment, security boundaries, and supported voice architectures are not the same.

Compliance and Regulatory Alignment

The most important distinction between GCC and GCC High for Teams Phone is regulatory coverage.

GCC is acceptable for organizations whose voice communications fall under FedRAMP Moderate–level requirements and do not involve export-controlled data or defense-related obligations. This includes many civilian agencies, state and local governments, and contractors working on non-DoD programs. In these environments, Teams Phone can be deployed without the additional compliance controls required for national security workloads.

GCC High is required when Teams Phone is used in environments subject to ITAR, DFARS, CMMC, or export-control regulations. Microsoft explicitly limits ITAR-aligned language and support to GCC High because these requirements depend on stronger isolation, stricter access controls, and assurances that cannot be met in GCC. For defense contractors and DIB organizations, using GCC instead of GCC High for voice can introduce compliance gaps, even if collaboration workloads appear to function normally.

Security and Data Sovereignty

Security and data sovereignty are enforced differently in GCC and GCC High, and those differences matter more for voice than for collaboration alone.

GCC relies primarily on logical separation within Microsoft’s government cloud framework. While data residency and access controls are aligned with government requirements, the environment does not provide the same level of physical and operational isolation as GCC High.

GCC High, by contrast, runs entirely within Azure Government, which is both physically and logically isolated from commercial Microsoft cloud infrastructure. Access to systems and customer data is restricted to U.S.-citizen Microsoft personnel who undergo enhanced screening, a requirement that is especially relevant when handling voice traffic and call metadata.

Voice metadata, such as call records, signaling information, voicemail, and emergency services data, often falls under stricter scrutiny than chat or meeting content. GCC High’s security model is designed to ensure that this information remains within U.S.-only systems and under access controls that meet defense and export-control expectations.

Feature Availability and Limitations

Teams Phone is available in both GCC and GCC High, but feature availability and delivery models differ from each other.

In GCC High, Teams Phone is supported only through Direct Routing. Microsoft Calling Plans and Operator Connect are not available, which means organizations must use a compliant carrier and SBC architecture that aligns with Azure Government. This requirement adds planning and architectural considerations that don’t exist in GCC or commercial environments.

Both GCC and GCC High also differ from commercial Teams in terms of feature parity. Some calling features, integrations, or updates may be delayed, modified, or unavailable due to compliance requirements. These limitations are intentional trade-offs to meet government security and regulatory standards.

Who Should Choose GCC for Teams Phone?

GCC is a good fit for organizations that want to enable Teams Phone in a government-aligned environment without overbuilding for compliance they don’t actually need.

GCC may be sufficient if:

• Your organization supports civilian federal, state, or local agencies
• PSTN calling is limited to administrative or non-defense workflows
• Your contracts do not involve export-controlled or defense-regulated data
• FedRAMP Moderate satisfies your compliance requirements

Who Should Choose GCC High for Teams Phone?

GCC High is designed for organizations where voice communications fall within the scope of defense or export-controlled requirements, and where choosing incorrectly can create long-term compliance risk.

GCC High is typically required if:

• You are a DoD contractor or part of the Defense Industrial Base (DIB)
• Your contracts reference ITAR, DFARS, or CMMC obligations
• PSTN calling supports or touches regulated workflows or sensitive programs
• Your environment requires U.S.-only data residency and U.S.-citizen access controls
• Migrating Teams Phone later would be costly, disruptive, or risky

For these organizations, starting in GCC High avoids compliance gaps and prevents the need for a complex re-architecture after voice services are already in production.

Cost and Complexity Considerations

GCC High deployments are almost always more expensive and complex than GCC. You need to factor in the licensing costs, additional controls, and operational requirements needed to support national-security and export-controlled workloads.

Several factors contribute to the higher cost of Teams Phone in GCC High. The environment runs on Azure Government, which is physically and logically isolated from Microsoft’s commercial cloud. Access is restricted to U.S.-citizen, screened personnel, and services are designed to meet FedRAMP High, ITAR, DFARS, and CMMC requirements. For voice, this also means Direct Routing is mandatory, adding carrier, SBC, and architectural considerations that don’t exist in commercial environments.

This added complexity often requires more planning, tighter coordination between IT, compliance, and telecom teams, and greater reliance on specialized providers who understand GCC High constraints. As a result, deployments tend to take longer and involve higher ongoing operational costs than equivalent Teams Phone rollouts in GCC.

That said, cost should be evaluated in the context of compliance risk. For organizations that require GCC High, choosing a lower-cost environment upfront can lead to regulatory exposure, audit findings, or a forced migration later. These things make it far more expensive and disruptive than deploying the correct environment from the start.

How Atlantech Supports Teams Phone in GCC and GCC High

Deploying Teams Phone in government environments (particularly in GCC High) requires compliant PSTN access, the correct Direct Routing architecture, and hands-on experience with Azure Government and federal compliance requirements. Atlantech supports Teams Phone in both GCC and GCC High with services designed specifically for these environments.

Atlantech provides secure, U.S.-based PSTN calling for Microsoft Teams that aligns with government and DoD requirements around data residency, access controls, and regulated communications. In GCC High environments, this includes support for organizations subject to CMMC, DFARS, and ITAR, helping ensure that voice traffic and call metadata remain within approved U.S.-only systems and operational boundaries.

Because Direct Routing is the only supported method for Teams Phone in GCC High, Atlantech delivers Direct Routing as a managed service. It provides certified Session Border Controllers (SBCs), handles PSTN connectivity, and supports enterprise calling features such as emergency calling, call queues, and conferencing within Microsoft Teams. Experience across both GCC and GCC High environments helps reduce risk during deployment and avoids common misconfigurations that can occur when commercial voice designs are applied to government clouds.

Atlantech also supports organizations through the planning, migration, and onboarding of Teams Phone, including number porting, policy configuration, and user enablement. We also offer guidance aligned to government and defense compliance requirements. Our goal is to help Teams Phone deployments stand up not only at launch, but also under audits, contract reviews, and long-term operational scrutiny.

Choose the Right Cloud for Government Voice

Microsoft Teams Phone can be a powerful tool for government organizations, but only when it’s deployed in the right cloud environment. Your cloud decision shouldn’t be based on features or pricing. Start with compliance boundaries and work backward. Understand where your voice traffic lives, who can access it, and which regulations apply to determine whether GCC is sufficient for your needs or whether you need to consider GCC High.

Take the time to validate this decision early on and avoid downstream risk, re-architecture, and compliance issues that are far harder to fix once Teams Phone is live.

If you want help validating your Teams Phone architecture or confirming which government cloud aligns with your compliance requirements, talk to one of our government voice experts before you deploy at scale.