Microsoft Teams Virtual Session Border Controller

Session Border Controller Service for Microsoft Teams or Microsoft Phone System

Telephony connectivity for your Microsoft Teams or Microsoft Phone Systems users to your preferred PSTN/ SIP providers using Direct Routing, without purchasing or installing any hardware Session Border Controller (SBC). Using direct routing alongside or rather than a Microsoft Calling Plan allows you to purchase the best rates available in your respective market. You can also add multiple SIP trunks in each geography to reduce calling costs.

Freeswitch, FusionPBX

Our SBC is a virtual cloud-based service that you use on a monthly per-channel base without any upfront commitment at 3$ per channel per month and 150$ setup fee per SIP interconnectivity (one operator, one SIP-ISDN gateway,...).

The redundant SBC allows you to purchase phone numbers and phone traffic from your preferred operators in any country. If you frequently place international calls to  certain countries, you can also integrate with several local operators to reduce your international calling charges.

If you have very small branches, and SIP connectivity is not available or affordable, you can buy a SIP-ISDN (with a BRI or PRI) or SIP-Analog gateway in your local market (starting at 200 USD for a BRI) and then use our SBC to connect your Microsoft Teams installation to your operator: This also allows you to purchase fewer phone numbers from the operator than you have Microsoft Teams users.

Advanced Voice Features

Advanced voice features that are easier to implement in a separate IPT environment include:

With our virtual SBC, users from Microsoft Teams can reach IP-PBX users that have more advanced features and vice versa.

Expertflow provides advanced voice features as SaaS, in it's cloud UCCaaS offering.


Microsoft Teams is a very powerful solution in the B2B sector, where you primarily interact internally in teams across multiple channels. It has, however, limitations in B2C interactions where you interact primarily with external users, and where the main tool used is not Teams but for example a CRM (or where a Teams license would be too costly).

In such scenarios, you typically need a separate PBX (Experflow provides on-prem Cisco UCCX/ PCCE/ UCCE or cloud-based Freeswitch/ FusionPBX), which can provide such functionality.

Microsoft Graph API

Microsoft Teams is continuously rolling out new features, so it might be that at some point it can provide features similar to a dedicated IP-PBX (albeit at a certain cost).

Many of the above features can be made available through the Microsoft Graph API, and Expertflow might release features that it currently only provides only on Cisco or Freeswitch and also on Microsoft Teams.

Besides SIP and telephony connectivity between Microsoft Teams and an IP-PBX, companies might want to see logical information. For example, an agent in a call center using in a Cisco case Finesse (UCCX, PCCE, UCCE), or Expertflow's Cloud Callcenter could see users of Microsoft Teams, without actually requiring a Microsoft Teams license, or without requiring a Microsoft Teams license. Such IP-PBX users would not have the capabilities of teams or require a telephony license, but they could still interact with them. Such a scenario would make sense if you have dedicated call center users who from time to time need to reach out to Microsoft Teams users, or forward calls to the same.

Prerequisites and pricing

Either one of the following configurations:

  • Microsoft E1, E3, or Business Basic with Microsoft Teams plus Phone System
  • Microsoft Office 365 plus Business Voice
  • Microsoft E5

The additional Microsoft Business Voice license cost is approx. 8 USD per user per month.

You are responsible for:

  • configuring Microsoft Teams
  • ensure sufficient bandwidth and QoS between your Microsoft Teams users and your operator.

Voice Traffic is not transiting through the Expertflow SBC (it only handles signaling), and calls are encrypted end-to-end between your premises and your operator, so we can't control voice quality. Our SBC is not certified by Microsoft Teams as SBC, but we behave like a compliant SBC towards MS Teams.