Voice - Phone System and PSTN connectivity options

You've completed Get started. You've rolled out Teams with chat, teams, channels, & apps across your organization. Maybe you've deployed Meetings & conferencing. Now you're ready to add voice capabilities for your users.

Voice provides Private Branch Exchange (PBX) capabilities, and options for connecting to the Public Switched Telephone Network (PSTN).

This article helps you decide whether you need to change any of the default voice settings, based on your organization's profile and business requirements, then it walks you through each change. We've split the settings into two groups, starting with the core set of changes you are more likely to make. The second group includes the additional settings you may want to configure, based on your organization's needs.

We recommend that all organizations work through the core decisions and then, if your organization has additional requirements, review the following material.

Learn more about voice

The following articles provide more information about deploying and using voice features in Teams:

Core deployment decisions

These are the settings that most organizations want to change (if the Teams default settings don't work for the organization).

Phone System (Office 365)

Phone System is Microsoft's technology for enabling call control and Private Branch Exchange (PBX) capabilities in the Microsoft 365 or Office 365 cloud. Phone System allows you to replace your existing Private Branch Exchange (PBX) system with a set of features directly delivered from Microsoft 365 or Office 365 and tightly integrated into the company's cloud productivity experience.

Ask yourself Action
In which user locations or offices will I implement Phone System? For more information about Phone System, see What is Phone System in Microsoft 365 or Office 365.

Connection to the Public Switched Telephone Network (PSTN)

To connect Phone System to the Public Switched Telephone Network (PSTN) so that users can make phone calls around the world, you have options based on your business need. Ask yourself the following:

Ask yourself Action
Do I want to use Microsoft Calling Plan as my telephony carrier? For more information, see Phone System with Calling Plans.
Do I need to use my own telephony carrier? For more information, see Phone System with Direct Routing.

Additional deployment decisions

You may want to change settings for the following, based on your organization's needs and configuration:

  • Voicemail
  • Calling identity
  • Phone numbers from Microsoft
  • Dial plans
  • Call queues
  • Auto attendants


Cloud Voicemail, powered by Azure Voicemail services, supports voicemail deposits to Exchange mailboxes only and doesn't support third-party email systems. Cloud Voicemail includes voicemail transcription, which is enabled for all users in your organization by default. Your business needs might require that you disable voicemail transcription for specific users or everyone throughout the organization.

Ask yourself Action
Do I want to enable Cloud Voicemail? For voicemail setup procedures, see Set up Cloud Voicemail.
Do I want to enable voicemail transcription for some or all of my users? To turn off voicemail transcription, see Setting voicemail policies in your organization.

Calling identity

By default, all outbound calls use the assigned phone number as calling identity (caller ID). The recipient of the call can quickly identify the caller and decide whether to accept or reject the call.

Ask yourself Action
Do I want to mask or disable caller ID? To change or block the caller ID, see Set the caller ID for a user.

Phone numbers from Microsoft

Microsoft has two types of telephone numbers available: subscriber (user) numbers, which can be assigned to users in your organization, and service numbers, available as toll and toll-free service numbers, which have higher concurrent call capacity than subscriber numbers and can be assigned to services such as Audio Conferencing, Auto Attendants, or Call Queues.

Ask yourself Action
Which user locations need new phone numbers from Microsoft? For information about getting phone numbers, see Manage phone numbers for your organization and Getting phone numbers for your users.
Which type of telephone number (subscriber or service) do I need? To help you pick the type of phone number you need, see Different kinds of phone numbers used for Calling Plans.
How do I port existing phone numbers to Teams? For more information, see Transfer phone numbers to Microsoft Teams.

Dial plans

A dial plan in the Phone System feature of Microsoft 365 or Office 365 is a set of normalization rules that translate dialed phone numbers into an alternate format (typically E.164 format) for call authorization and call routing.

For more information about dial plans, see What are dial plans?

Ask yourself Action
Does my organization need a customized dial plan? To help determine if you need a custom dial plan, see Planning for tenant dial plans
Which users require a customized dial plan, and which tenant dial plan should be assigned to each user? To add users to a customized dial plan in PowerShell, see Create and manage dial plans.

Call queues

Cloud call queues include greetings that are used when someone calls in to a phone number for your organization, the ability to automatically put the calls on hold, and the ability to search for the next available call agent to handle the call while the people who call are listening to music on hold. You can create single or multiple call queues for your organization.

Ask yourself Action
Does my organization need call queues? For more information, see Create a Cloud call queue and Setting up your Phone System.

Auto attendants

Cloud auto attendants can be used to create a menu system for your organization that lets external and internal callers move through a menu system to locate and place or transfer calls to company users or departments in your organization.

Ask yourself Action
Does my organization need auto attendants? For more information, see What are Cloud auto attendants and Set up a Cloud auto attendant.


For more information about supported devices, see the following: