VoIP and Microsoft 365: Integrating Calling with Teams

How VoIP Integrates with Microsoft 365

Microsoft 365 Business plans include Microsoft Teams, which already handles internal calling, video meetings, and team chat. The missing piece for most businesses is external calling — the ability to dial a standard UK phone number and receive calls from clients and contacts. This is where Teams Phone comes in.

Teams Phone adds a PSTN calling layer to Teams. Once enabled, staff can dial any UK or international number directly from the Teams interface, receive calls to their business number on Teams, and manage calls, voicemail, and transfers through the same application they already use for internal communications. There is no separate phone app to learn and no additional hardware required beyond what staff already have.

Microsoft Calling Plans vs Direct Routing

There are two ways to add PSTN calling to Microsoft Teams. Microsoft Calling Plans is Microsoft's own phone number and call routing service — you buy phone numbers and calling minutes directly from Microsoft. It is simple to set up but typically more expensive per minute than third-party carriers, and number porting from an existing provider can be slower.

Direct Routing connects Teams to a third-party SIP trunk provider — such as the carrier your business already uses, or a new provider selected by AMVIA. Your existing phone numbers are ported to the SIP provider and calls are routed through Teams via an Azure-certified session border controller. Direct Routing typically offers lower per-minute costs and more flexibility. AMVIA manages the session border controller and SIP carrier relationship on your behalf.

Why This Integration Matters for UK Businesses

Integrating VoIP with Microsoft 365 simplifies your IT stack. Instead of maintaining a separate phone system alongside Microsoft 365, everything lives in one platform. Call history integrates with Teams chat history. Voicemail arrives in your Teams inbox alongside messages and notifications. Contacts sync from Outlook. For a business already deeply embedded in Microsoft 365, removing a separate phone system reduces complexity and cost.

With BT's PSTN switch-off deadline of 31 January 2027, businesses with ISDN-connected phone systems must migrate regardless. For businesses already on Microsoft 365, Teams Phone is often the most cost-effective and integrated migration path — eliminating both ISDN lines and the separate phone system in a single transition.

Key Considerations for UK SMEs

• Check your Microsoft 365 licence: Teams Phone requires a Teams Phone licence add-on (approximately £8 per user per month) on top of your existing Microsoft 365 subscription. Not all Microsoft 365 plans include it automatically.
• Direct Routing requires a session border controller: If using Direct Routing rather than Microsoft Calling Plans, an Azure-certified session border controller is required. AMVIA manages this as a service — it is not a hardware device you need to purchase.
• Number porting takes time: Porting existing geographic numbers to a Teams-compatible SIP carrier typically takes 7 to 14 working days. Plan this carefully to avoid any service gap.
• Internet connection quality matters: Teams calls require a stable, low-latency internet connection. AMVIA assesses your connectivity before migration to ensure it will support the call volume you require.

How AMVIA Can Help

AMVIA configures and manages Microsoft Teams Phone for UK businesses using Direct Routing — including session border controller management, SIP carrier selection, number porting, and ongoing support. AMVIA also handles the Microsoft licencing, ensuring you have the right Teams Phone add-on for the right users. Call 0333 733 8050 to discuss how Teams Phone can work for your business.