Best GCC High Voice Carriers (2026 Edition)

Microsoft GCC High is a popular collaboration platform among government and defense organizations. It’s designed for teams that need to meet strict compliance requirements, and it’s often the default choice for handling regulated work inside Microsoft 365.

But GCC High has one major limitation: it does not include phone service. You can’t make or receive external phone calls in Microsoft Teams using Microsoft Calling Plans or Operator Connect, because those options aren’t supported in GCC High.

If your organization needs PSTN or Teams Calling, you have to connect Teams to a third-party voice provider using Direct Routing. This is where many teams run into trouble.

Not all voice providers support GCC High. Some only work in commercial Microsoft 365, others aren’t suited for ITAR or DFARS-regulated environments, and many don’t fully understand Azure Government architecture. Choosing the wrong provider often means failed deployments, additional compliance reviews, or having to redesign the voice setup after it’s already in place.

In this guide, we break down the best GCC High voice providers using verified Atlantech Online content and public, source-safe descriptions of each provider. We’ll help you confidently choose a compliant PSTN option for Microsoft Teams in GCC High.

How We Chose These Providers

There is no official marketplace or certification list for GCC High voice providers. As a result, many vendors claim to support Teams Calling without clearly stating whether they can operate inside Azure Government or meet the compliance expectations that come with GCC High.

To avoid this guesswork, we evaluated providers using the following criteria:

GCC High Readiness

First, providers had to demonstrate the ability to deliver PSTN calling via Direct Routing in GCC High. Because Microsoft Calling Plans and Operator Connect are not supported in GCC High, any provider that operates only in commercial Microsoft 365 environments was excluded.

Compliance Fit

We prioritized providers with experience supporting regulated workloads, including environments that require alignment with CMMC, DFARS, ITAR, or similar frameworks. This does not mean every provider explicitly certifies compliance, but they must be positioned to operate in environments where those requirements apply.

U.S. Infrastructure and Personnel Requirements

GCC High environments are built on U.S.-only data pathways and are supported by U.S.-screened personnel. We’ve evaluated providers on whether their infrastructure, routing model, and support operations align with those expectations.

Track Record in Government or GCC High Environments

We favored providers with an established presence in government or GCC High deployments, including documented partnerships, long-standing Direct Routing implementations, or recognized experience supporting federal contractors.

Support Model and Deployment Experience

Finally, we looked at how providers support customers in practice. This includes U.S.-based support, onboarding and migration guidance, and hands-on experience deploying Teams Phone with Direct Routing for DoD contractors and regulated organizations.

The 6 Best GCC High Voice Providers

Below are six voice providers that support Microsoft Teams Direct Routing in GCC High, each with different strengths depending on compliance needs, deployment style, and scale.

CallTower — Established GCC High Direct Routing Provider

Best for: Organizations looking for a Microsoft Teams Direct Routing provider with a proven operational history in GCC High.

CallTower was one of the earliest providers to support Direct Routing in GCC High, with live deployments in production environments since 2019. In regulated government and contractor settings, that history is significant because many GCC High-specific constraints (such as tenant isolation, routing design, and compliance validation) only become visible once a solution has been operating over time.

Why it’s a strong option: CallTower supports Teams Phone deployments in regulated environments, including projects that require careful coordination with Microsoft, government tenants, and third-party systems. Its track record in GCC High suggests familiarity not just with initial setup, but with the operational realities of running voice services through Azure Government over the long term. CallTower is also well established within the Microsoft partner ecosystem, which can be beneficial for larger or multi-vendor deployments.

Potential drawbacks: CallTower is a broad enterprise voice provider. While it supports GCC High Direct Routing, organizations with very specific ITAR- or DFARS-focused compliance requirements may need to confirm that their needs can be met within a larger, generalized service model.

HelloTeams — Fast, Automated GCC High Deployments

Best for: Organizations that want to enable Teams Phone in GCC High quickly, with minimal manual configuration and a more guided onboarding experience.

HelloTeams focuses on simplifying Direct Routing deployments for Microsoft Teams, including GCC High environments. It uses automation to reduce setup time and configuration effort. This approach is particularly appealing to government contractors moving off legacy PBX or traditional VoIP systems and looking for a faster path to production.

Why it’s a strong option:  HelloTeams is designed around automated workflows that handle much of the complexity involved in configuring Teams Phone for GCC High. Its services are built for government environments, with a U.S.-based infrastructure and support model aligned to GCC High expectations. For organizations that prioritize speed, predictability, and a standardized deployment model, this automation can significantly shorten rollout timelines and reduce internal effort.

Potential drawbacks:  Because HelloTeams emphasizes automation and standardized deployment patterns, it may be less flexible for highly customized call routing or non-standard voice architectures. Organizations with complex, bespoke telephony requirements may need to confirm that automation-first workflows can accommodate their needs.

Momentum Telecom — Secure PSTN Access for GCC High

Best for: Organizations that prioritize a strong security and compliance posture and need reliable PSTN access for Microsoft Teams in GCC High.

Momentum Telecom is a provider that supports secure, regulated voice environments, including GCC High. Its approach is geared toward organizations that want a voice architecture aligned closely with Azure Government constraints and compliance expectations, rather than a lightly adapted commercial model.

Why it’s a strong option: Momentum offers compliant PSTN connectivity for Microsoft Teams in GCC High through a dedicated provider model that reflects how GCC High environments are structured. This includes an emphasis on secure routing, controlled infrastructure, and operational practices suitable for government and defense contractors. For organizations that view voice as part of a broader security and compliance strategy, Momentum’s focus can be a good fit.

Potential drawbacks: Momentum Telecom is typically used by mid-sized to large deployments, where security requirements and call volumes justify a more structured provider relationship. Smaller teams or organizations looking for a lightweight or highly automated rollout may find this modet too dense for their needs.

Atlantech Online — Compliance-Focused GCC High Direct Routing

Best for: DoD contractors and regulated organizations that need explicit support for CMMC, DFARS, and ITAR when enabling Microsoft Teams Calling in GCC High.

Atlantech Online positions its GCC High voice offering specifically around regulated government and defense workloads, rather than adapting a commercial voice platform for government use. This makes it a strong option for organizations where compliance requirements are not just contextual, but central to the deployment.

Why it’s a strong option: Atlantech Online provides a Microsoft Teams Calling solution purpose-built for GCC High, with Direct Routing delivered as a managed service. Because Direct Routing is required in GCC High, Atlantech’s DRaaS model removes much of the architectural and operational burden from internal IT teams that use it.

Atlantech is a solution that is compliant with CMMC, ITAR, and DFARS requirements, and operates using U.S.-based infrastructure and support teams familiar with the constraints of Azure Government. This compliance-first approach, combined with hands-on experience supporting GCC High tenants, makes Atlantech particularly relevant for organizations that need voice services to stand up to audits, contract reviews, and long-term regulatory scrutiny. Atlantech Online’s MS Teams Phone for GCC High Infrastructure is also compliance-ready and can be provided to an organization as quickly as 2 weeks.

Potential drawbacks: Atlantech operates as a regional fiber and voice provider, which is a strength for reliability and service control, but means it is less globally distributed than large multinational carriers. Organizations with extensive international telephony requirements may need to account for that difference.

Aura Connect — GCC & GCC High Voice via U.S. Data-Sovereign Infrastructure

Best for: Organizations operating across both GCC and GCC High that want a consistent voice solution without managing separate providers for each environment.

Aura Connect focuses on delivering voice services designed specifically for government cloud environments, with support for both GCC and GCC High. This is useful for organizations that operate in both environments and want the same voice setup in both.

Why it’s a strong option: Aura Connect offers voice solutions built on U.S.-only, data-sovereign infrastructure that is purpose-built for compliance-driven environments. It regulates workloads and government contractors, rather than general enterprise telephony. For organizations managing both GCC and GCC High environments, Aura Connect’s ability to support voice consistently across both tiers can reduce operational complexity and governance overhead.

Potential drawbacks: Aura Connect has a smaller brand presence in the U.S. market compared to larger providers like CallTower or Momentum. Organizations may need to spend additional time validating references, scale, or long-term footprint, depending on their deployment size and risk tolerance.

C3 Integrated Solutions — GCC High Partner with Voice Enablement

Best for: Organizations that want hands-on help migrating to GCC High, with voice services delivered through a trusted partner rather than managed directly.

C3 Integrated Solutions is best known for the way it handles GCC High migrations, as well as its compliance readiness and secure cloud architecture in government and defense environments. Rather than operating its own voice infrastructure, C3 works through established partners to enable calling inside GCC High.

Why it’s a strong option: C3 helps organizations prepare for and move into GCC High. The team guides compliance and secure cloud posture. For voice services, C3 partners with CallTower to deliver PSTN calling and conferencing within GCC High. This model can work well for organizations that want migration, compliance, and voice enablement handled together, especially if they value a single consulting-led engagement.

C3 is also well known within the CMMC and Defense Industrial Base (DIB) community, which can be reassuring for organizations navigating compliance-driven cloud transitions.

Potential drawbacks: Because C3 delivers voice services through a partner model, it does not operate its own native voice infrastructure. Organizations that prefer a single, direct voice provider may want to factor this into their decision.

Expert Recommendations: Which GCC High Voice Provider Is Best for You?

The right GCC High voice provider for your organization depends on how regulated your environment is, how you plan to deploy Teams Phone, and whether voice is a standalone requirement or part of a broader compliance effort.

Here’s how these providers typically map to real-world needs.

Choose Atlantech Online if you:

Need explicit support for CMMC, DFARS, and ITAR in a GCC High environment

Choose CallTower if you:

Want the longest-running track record supporting Direct Routing in GCC High

Need a provider proven at large or complex Teams Phone rollouts

Prefer working within a mature Microsoft partner ecosystem

Choose HelloTeams if you:

Need a fast, automated rollout of Teams Phone in GCC High

Want a simpler onboarding experience with minimal manual configuration

Are moving off legacy PBX or VoIP and value speed over customization

Choose Momentum Telecom if you:

Prioritize a strong security and compliance posture for voice services

Need enterprise-grade PSTN aligned with GCC High architecture

Are planning a mid-sized or large deployment where structure matters

Choose Aura Connect if you:

Operate across both GCC and GCC High tenants

Want a consistent voice setup across government cloud tiers

Prefer a provider focused on data sovereignty and regulated environments

Choose C3 Integrated Solutions if you:

Need GCC High migration consulting alongside voice enablement

Want compliance, cloud readiness, and voice handled through a partner-led model

Are navigating CMMC or DIB requirements and value hands-on guidance

Need Help Deciding?

When choosing a GCC High voice provider, you want a solution that balances compliance requirements, Teams Phone architecture, and Direct Routing inside Azure Government. 

If you’ve reviewed our recommendations but still need help finding the best fit for your organization, or if you need guidance on enabling PSTN calling for Microsoft Teams in GCC High, you can request a consultation with Atlantech’s team.