This script will allow you to automate Lync (Skype for Business) number assignment. It will update the user's number in Lync, as well as AD.

ModifyUserLyncNumber.ps1

#############################
#  Modify User Lync Number  #
#############################
<#
Description: 
This script will allow you to automate Lync (Skype for Business) number assignment.
It will update the user's number in Lync, as well as AD.
If you use a spreadsheet to track number assignment you'll want to add sections to update that as well.

Prereqs:
Make sure the server running the script has the ActiveDirectory Module installed
The running account will also need AD edit permissions
The account will also need Lync edit permissions

Future Consideration:
- Include a switch and then if true, add voicemail as well (need Exchange permissions in that case)
- Consider checking to see if the user is Lync enabled or not? - "Enable-CsUser"
#>

Function ModifyUserLyncNumber {
    param (
    [string]$userName = "TestUser",
    [string]$action = "Add",
    [string]$newNumber = "123-123-1234"
    )
    #Grab an AD reference to the user to modify
    $Employee = ''
    $ADObject = Get-ADUser $userName -Properties *
    if($ADObject)
    {
        $Employee = $ADObject
    }
    else
    {
        Write-Output "No user was found!"
    }
    #Create a Lync connection for later use
    $session = New-PSSession -ConnectionUri https://<YOUR.LYNC.WEB.LOCATION.HERE>/OcsPowershell -Authentication Negotiate
    try
    {
        if($action -eq "Add")
        {
            #Double check to make sure they don't currently have a number assigned
            $oldNumber = ""
                #Connect to Lync
                Import-PsSession $session
                $csUser = Get-CSUser $Employee.SamAccountName
                #End the Lync Connection
                $oldNumber = $csUser.LineURI
                if($oldNumber)
                {
                    Write-Output "The selected employee already has an assigned number."
                }
                else
                {
                    #Format the number for Lync as "tel:+11231234567"
                    $newLyncNumber = "tel:+1" + ($newNumber -replace '[-]','')
                    Set-CsUser -Identity $Employee.UserPrincipalName -LineUri $newLyncNumber -EnterpriseVoiceEnabled $True
                }
                Remove-PsSession $session
            #If The user doesn't already have an assigned number, continue
            if(!$oldNumber)
            {
                #Set the Number in the AD field
                Set-ADUser $Employee.SamAccountName -OfficePhone $newNumber
                Write-Output "Number has been added successfully"
            }
        }
        elseif($action -eq "Remove")
        {
            $oldNumber = ""
                #Connect to Lync
                Import-PsSession $session
                #Get the users current number
                $csUser = Get-CSUser $Employee.SamAccountName
                $oldNumber = $csUser.LineURI
                #Remove the number in Lync
                Set-CsUser -Identity $Employee.UserPrincipalName -LineUri $null -EnterpriseVoiceEnabled $False -AudioVideoDisabled $False -RemoteCallControlTelephonyEnabled $False
                #End the Lync Connection:
                Remove-PsSession $session
            #Remove the number in AD
            Set-ADUser $Employee.SamAccountName -OfficePhone $null
            Write-Output "Number has been removed successfully"
        }
        elseif($action -eq "Change")
        {
            #Format the number for Lync as "tel:+13061234567"
            $newLyncNumber = "tel:+1" + ($newNumber -replace '[-]','')
            $oldNumber = ""
                #Connect to Lync
                Import-PsSession $session
                $csUser = Get-CSUser $Employee.SamAccountName
                $oldNumber = $csUser.LineURI
                #Set the Number in Lync
                Set-CsUser -Identity $Employee.UserPrincipalName -LineUri $newLyncNumber -EnterpriseVoiceEnabled $True
                #End the Lync Connection:
                Remove-PsSession $session
            #Remove the number in AD
            Set-ADUser $Employee.SamAccountName -OfficePhone $newNumber
            Write-Output "Number has been changed successfully"
        }
    }
    catch
    {
        Write-Output "$($_.Exception.Message) (At line $($_.Exception.Line), character $($_.Exception.Offset))"
    }
}