powershell set-aduser help.

I need to input ipphone for every user in the AD.  (windows 2008 R2 DCs)

The users.csv file is this format:(username is the samaccount)

username, ipphone

user1,123-456-8900

user2,123-456-9900

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Import-CSV "C:\Scripts\Users.csv" | % {
$User = $_.UserName
$ip = $_.ipphone
Set-ADUser $User -ipphone $ip
}

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I got "a parameter can not be found that matches parameter ipphone ..."

Can anyone help?

Thank you.