Hi Sarah,
Sorry for the trouble! Your Skype extension or plugin will do this automatically for all phone numbers. The only way to keep this from happening is to disable the extension. I'm sorry for the trouble. This Skype article talks about how to remove this: http://community.skype.com/t5/Other-features/How-to-Disable-or-Remove-the-Click-and-Call-Function/m-p/69602/message-uid/69602#U69602