If you haven't already done this, I would verify that the $_.telephonenumber had a value.
ForEach...{$_.samAccountName
$_.telephoneNumber}
This ensures you haven't spelt something wrong or some other issue that isn't populating the variable
Paul Bergson
MVP - Directory Services
MCITP: Enterprise Administrator
MCTS, MCT, MCSE, MCSA, Security, BS CSci
2012, 2008, Vista, 2003, 2000 (Early Achiever), NT4
Twitter @pbbergs http://blogs.dirteam.com/blogs/paulbergson
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