Unassign Service number from Conference Bridge

In Skype for Business admin center, you have the option to use one of your Service Numbers as default Conference Bridge number instead of the default shared number.

However, if you changed your mind and wish to unassign this number and use it for a different purpose, you might notice that the Unassign button is greyed-out and while hoovering over it, you are redirected to contact Support.

There is a workaround to do this by yourself, and all you need is Windows PowerShell and the Skype for Business Online Windows PowerShell Module available here.

Getting Started:

1.Connect to Skype for Business Online by using Windows PowerShell. (https://technet.microsoft.com/en-us/library/dn362795(v=ocs.15).aspx)

2.Obtain the name of the Bridge by running the following cmdlet:

3. Unregister-CsOnlineDialInConferencingServiceNumber -BridgeName “Conference Bridge” -RemoveDefaultServiceNumber 1234 // where 1234 should be replaced by the number you wish to unregister.

4. Go back to the Skype for Business admin center and check if the number has been unassigned:


User and Service numbers

In Office365, you can get two types of numbers: User numbers and Service number. Well, if the naming isn’t explanatory enough for you, I’ll elaborate this subject below. 

While User numbers can only be assigned to user accounts (you@yourdomain.tld), Service number cannot be assigned to users, but to services like: Auto Attendant, Call Queues or Conferencing Bridges. 

Aside the purpose, there are also capacity differences between these numbers. While User numbers can only handle a few simultaneous calls, Service numbers can handle hundreds of calls simultaneously. 

To get a better picture on Service number, imagine you call your mobile phone Carrier and you hit the Interactive Voice Response. Next to you, most likely other users are dialing that very same number and wonder around the IVR, so that Service number better be ready to handle a lot of Simultaneous calls. 

A little more info on: 

User numbers: 

Available for: 

  • Belgium 
  • Canada 
  • France 
  • Germany 
  • Ireland 
  • Netherlands 
  • Spain 
  • United kingdom 
  • US & Puerto Rico 


SfBOnline/Microsoft Teams license + Phone System + Domestic/International Calling + Communication Credits (optional). 

 Please note that if you go with “E-packs”, E5 already includes SfBOnline, Microsoft Teams and Phone System licenses, so you’ll only have to get Domestic or International Calling license and optionally Communication Credits (get it if you plan to dial destinations where included minutes don’t permit calling). 

 Regarding how many numbers you can acquire, you should know that it depends on the number of licenses you have. The formula is: 

Domestic and/or International Calling license * 1.1 + 10 

 So, if you have 5 Domestic Calling licenses and 5 international Calling ones, you can get: 


 Getting the numbers: 

At the time of writing this one, numbers are still to be acquired from the “old” Skype for Business Admin Center -> Voice -> Phone numbers. 

!note that you will only be able to get phone numbers for the countries where Domestic/International Calling is available: 



!note 2: For some countries like Belgium and Germany, you cannot purchase the numbers directly from the portal, so you’ll have to submit a number request to ptneu[at]microsoft.com. 

For this, access first this link and select the Country or region to find the appropriate number request. 

!note 3: Phone number in this scenario can only be granted to users via the GUI. 

In powershell, the online-acquired phone number is visible under the LineUri attribute if doing a get-csonlineuser. However, setting value to the LineUri attribute via set-csuser -identity “your user” -LineUri tel:+44xxx, will throw the following error message:
Unable to set “LineURI”. This parameter is restricted within Remote Tenant PowerShell. 

+ CategoryInfo          : InvalidArgument: (:) [Set-CsUser], ManagementException 

+ FullyQualifiedErrorId : LineURI,Microsoft.Rtc.Management.AD.Cmdlets.SetOcsUserCmdlet 

Be advised that a similar attribute holding phone value (OnPremLineUri) can be granted value via the set-csuser cmdlet, however, you should not do that for online-acquired numbers. 

The OnPremLineUri attribute will be setup with a phone number only in Hybrid-Voice scenarios, but that is a different discussion. 

!note 4: Getting Phone numbers also requires setting up an Emergency Location. Stay around for an article regarding this topic

The conclusion is: Online-acquired numbers should and will be granted to users only via the Skype for Business Online Admin Center. 


Service numbers: 

As I was writing at the beginning, Service numbers can handle a high number of incoming calls simultaneously and are assigned to services like: Auto Attendants, Call Queues or Conferencing Bridge.

We should note that Service numbers can also be:

  • Regular numbers
  • Toll-free numbers

Toll-free numbers are numbers which can be dialed locally at zero cost for the caller. However, since someone actually has to pay for the call, you will need Communication Credits setup and you will be charged for each incoming call.

To get an idea on the costs, visit Microsoft’s voice calling page, scroll down to “See rates for where you want to call” and select your country and currency. You will download a nice Excel which displays rates for both incoming (to toll-free service numbers) and outgoing calls. Don’t worry, incoming calls to user numbers or regular service numbers are not charged.

Available for:

Service numbers are available to acquire for quite alot of countries as you can see in the screenshot below:

However, to make sure Service numbers (regular or toll-free) are available for the country where you want to get them, visit Microsoft’s “Country and region availability for Audio Conferencing and Calling Plans” page and select from the drop-down menu the country:

As you can see, in Romania I cannot get Calling Plans (Domestic/International Calling), so no User numbers for me, but I can get instead Service numbers, both regular and Toll-free. Moreover, I can also get Communication Credits to cover the expenses if I go for a toll-free number:


In order to be able to acquire Service numbers, you have to have Phone System and/or Audio Conferencing licenses added to your tenant, and of course, if you wish to get toll-free numbers, then Communication Credits need to be added as well.

Regarding the number of Service numbers you can get, the math is simpler here:

Tenants with:

  • 1 – 25 licenses can get 5 Service numbers
  • 26 – 49 licenses can get 10 Service numbers
  • 50 – 99 licenses can get 20 Service numbers

The list goes up to 1500 service numbers, so if you wanna see exactly where your organization is positioning, have a look here.


How to change dial in conferencing number for SfB/Teams users

Picture the scenario where you need to change the default dial-in conferencing number for only part of the users within a tenant. That’s fine to do it manually if the numbering does not exceed 5-10 users, but we, IT guys, are lazy, so we’re going to do it from PowerShell anyway.

Needless to say that as pre-requisites you’ll have to have preferrably a Global Admin account and the Skype for Business Online Module for Powershell up and running:

First, make sure you have the Skype Online Connector installed. Get it from here.

Now, once the connector is installed on your machine, you can run all 4 lines at once in your PowerShell:

$credential = get-credential
Import-Module SkypeOnlineConnector
$lyncSession = New-CsOnlineSession -Credential $credential
Import-PSSession $lyncSession

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Now, we need a common attribute to collect in a variable all users for which we want to change the default Dial-in Conferencing number. In my lab, i’ve done this by querying the old number which I want to replace:

$user1 = Get-CsOnlineDialInConferencingUser | Where-Object {$_.ServiceNumber -ieq “old number here”}

Just to make sure we’re on the right track, we can call out the variable in order to check it’s contents.

Next step is to do a foreach loop here, changing the Dial-in Conferencing number for each object caught in our variable:
$user1 | foreach {Set-CsOnlineDialInConferencingUser -Identity $_.sipaddress -ServiceNumber “new number here”}


We have just sucesfully replaced one dial-in conferencing number with another for selected users.