Search for phone numbers for users
When you are setting up users in your organization to make and receive phone calls, you must use the Skype for Business admin center and first get phone numbers that can be assigned to users. The phone number you assign to a user will be a phone number that you have chosen for your organization and will be listed in the drop-down list when you edit the properties of the user and click Assign.
Before you can assign phone numbers to your users, you must use the New numbers page to search for numbers that are available for you within an area. You can search by Country/region, State, and City, and then enter the number of phone numbers you will need for your users.
If you need some help with getting phone numbers, you can see Manage phone numbers for your organization or Contact support for business products - Admin Help
Search for phone numbers
To search for phone numbers for your users
Using the Skype for Business admin center
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, and then click Add new number > New user 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 user numbers page, click the Country and State lists to select the state that you want to select numbers from, and then select the area code for the city from the City list.
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 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 user numbers you can acquire.
You can click Show numbers to see the full list of phone numbers. This is helpful is you don't want to select a specific phone number in the list.
Select the phone numbers you want ,and then click Acquire numbers.
You can acquire more phone numbers than you have licenses. To determine how many phone numbers you can acquire, take your number of licenses, add 10 percent of the number of licenses, and then add 10. For example, if you have 100 Domestic Calling Plan and/or International Calling Plan licenses, you can reserve 120 phone numbers, assuming that you have not already acquired some phone numbers for those 100 users. For more details, see How many phone numbers can you get?