Getting service phone numbers
In addition to getting phone numbers for your users from Office 365, you can search and acquire toll or toll-free phone numbers for services such as audio conferencing (for conference bridges), auto attendants, and call queues (also called service numbers). Service phone numbers have a higher concurrent calling capacity than user or subscriber phone numbers. For example, a service number can handle 100s of calls simultaneously, whereas a user's phone number can only handle a few calls simultaneously.
Office 365 Communications Credits must be set up first in order to acquire toll-free numbers. See Set up Communications Credits for your organization.
You have two ways of getting service numbers so you can use them with Skype for Business and Microsoft Teams:
Get new numbers from Office 365.
Port or transfer your existing numbers from your service provider or phone carrier to Office 365.
When you transfer your service numbers, it is highly recommended that you contact Microsoft support to ensure that the higher concurrent calling capacity is considered and configured correctly.
Get new service numbers
Sign in to Office 365 with your work or school account.
Go to the Office 365 admin center > Skype for Business.
In the left navigation go to Voice > Phone numbers > Add new number, and then click New service numbers.
For you to see the Voice option in the left navigation in the Skype for Business admin center, you must first buy at least one Enterprise E5 license, one Phone System add-on license, or one Audio Conferencing add-on license.
On the Add new service numbers page, choose the following:
Under Quantity, enter the number of phone numbers that you want for your organization and click Add to create a reservation. You have 10 minutes to select your phone numbers; if you take more than 10 minutes, the phone numbers will be returned to the pool of phone numbers.
You can see the number of phone numbers, which is based on the number of licenses, listed next to Total Service numbers your can acquire. For details, see How many phone numbers can you get?
You can click Show numbers to see the full list of phone numbers. This is helpful if you don't want to select a specific phone number in the list.
Select the phone numbers you want, and then click Acquire numbers.
Assign service numbers
Once you have your service numbers, they can then be assigned to an audio conferencing bridge. To do this, see Change the toll or toll free numbers on your Audio Conferencing bridge.
Port or transfer existing service numbers
If you want to transfer service numbers from your current service provider or carrier, you need to manually submit a port order to Microsoft. You have to submit separate port orders for each type of service number (toll vs. toll-free) that you will be transferring using a Letter of Authorization (LOA). In the Letter of Authorization (LOA), you must select the correct type of service number. When contacting Microsoft support, please make sure you specify that you are transferring a service number (and not a user or subscriber number), or the concurrent calling capacity may not be enough to handle call volumes. If you want to transfer phone numbers or do other things with your phone numbers, see Manage phone numbers for your organization.
If you need to get more telephone numbers than this, please contact support for business products - Admin Help.