Help formatting phone numbers using powershell

Hello,  I am trying to create a powershell to take all my users in active directory and format all of their phone numbers the same  (XXX)XXX-XXXX

I have the script getting the users and stripping all no numeric characters and writing the stripped number to the office phone field in AD.  however the formatting is not applying.  It does not error.  It just ignores it and writes the 10 digit number.

Here is the Powershell I am running. (this one has been modified to a single user for testing)

# Retrieve Single User
$Users =  Get-ADUser -LDAPFilter "(sAMAccountName=testuser)" -Properties sAMAccountName, telephoneNumber
ForEach ($User In $Users)
 {
     $Name  = $User.sAMAccountName
     # Replace non-digits with blank.
     $Phone = $User.telephoneNumber -Replace "[^0-9]", ""
     # Check length.
     If ($Phone.Length -eq 10)
     {
         # Format number as (xxx)xxx-xxxx
         $Phone= "{0:(###)###-####}" -f $Phone
         # Save corrected value for telephoneNumber.
         Set-ADUser -Identity $Name -OfficePhone $Phone
     }
     Else {"$Name invalid value: $Phone"}
 }