Strangely, I'm not shocked by this:

The actors hired by Premiere to provide the aforementioned voice talents sign confidentiality agreements and so would not go on the record. But their accounts leave little room for doubt. All of the actors I questioned reported receiving scripts, calling in to real shows, pretending to be real people. Frequently, one actor said, the calls were live, sometimes recorded in advance, but never presented on-air as anything but real.