Teams Business Voice and extensions

Copper Contributor

I am looking for some assistance if anyone can help out.


I am migrating our existing phone system to Business Voice and I am running into some issues getting extensions used how they used to be. Basically we have our main number (ex. 123456789) and I would like to be able to dial externally then input the extension (ex. 115) and reach that user. And internally just dial another users extension to reach them.


Here are a few specific things I am running into


Our auto attendant is set to dial by extension but I cant actually get it to route to a users extension

We have the users Office number field in Azure and O365 as 123456789;ext=115


For internal extensions I am looking for a way - maybe through dial plans? to get the input of the extension to go to the user as well. Note our auto attendant number and user numbers are separate meaning they extensions are not part of the main number in any way (1234567115) where we could just cut off part of the number.


Any advice would be greatly appreciated.

10 Replies



If you want to use Extension calling from an Auto Attendant it is the format +123456789;ext=789 you have to use.

Set up an auto attendant for Microsoft Teams - Microsoft Teams | Microsoft Docs


From a Teams client it is better to learn users how to call by name, ex. "/call <name>". But I guess you have desk phones that you want to use extension calling from, then in your Dial Plan you can setup this. But the extension have to match the number, so +123456789 would have extension 6789.

Use Extension Dialing in Microsoft Teams (

Thanks for the reply, internal extensions are quite as big of a deal if we just use contacts to call but do you have any recommendations for external callers reaching users via extension?

Not sure if you still need this, but in my case, I am utilizing unused -MobilePhone ext. (You will be required to install MSOnline module):


$cred = Get-Credential
Connect-Msolservice -Credential $cred
Set-MsolUser -MobilePhone ext=1001 -UserPrincipalName user@domain.tld

This way, user@domain.tld can be reached through Auto Attendant by dialling 1001, given the Auto Attendant setting is set to reach user by number.


Not sure if your query was answered. But the external people can call the Auto Attendant and then dial by Extension Feature to the reach the users via extension.

With Regards,
Satish U


Just a brief FYI to advise that this *does* work, but that you have to give Microsoft's back-end some time to process.  Additionally, I was able to add the ext=#### by simply logging into the M355 admin account and adding the information I needed in the field.  Again, it look some time for Microsoft to apply those changes, so be patient.

I can also confirm that while it does work on the "dial by extension" setting in Auto Attendant, it doesn't seem to work for dialing numbers internally.

A question: In the company where I work, the use of 7-digit extensions (XXXXXXX) is required. Is it possible to implement this range? For example: phone number "+34YYYYYYYYY;ext=XXXXXXX.
Thanks for your reply.

Yes that can be done but try to keep that 7 digit extension orgwide. 7 digit extensions should be unique and you can give the corresponding main number along with it. AA can handle those calls and you can cascade them if needed.

@M365_Teams What about the opposite: using Teams local app w Outlook Contacts local app (right click on Outlook client to call out) to dial outside recipients that can only be reached by navigating a fixed phone tree such as dial 2 for tech support, dial 5 for windows, dial 6 if you have a support contract.

Would be nice if same contact would all Outlook for Iphones and Android to auto navigate calls from the phones to those recipients. 


It already can be done with almost any phone system. You just have to know the next number need to be dialed. For example, if you know you will reach ext 1234 after the first greeting , then just save the phone on contact as +6221987654321,1234 (or you can add bash to make the dial immediate as +62219876321,1234#). And if you find out there are multiple greetings in the system, you just have to insert empty section between coma. For example there is a greeting then followed by language choice(1), then department choices(2), then sub department choice(5), so there are 3 greetings, then you would save the contact as +622198764321,1,,2,,5# so it can be right click dialed.
Does this work for you?
Me when i add anything to a number to dial out the call fails whenever so for example, 1-555-1234,,201 "dial-out" i get nowhere :(