I never got the feeling the products mentioned could be used in such a manner.

Also, telemarketers using pre-recorded lines is nothing new. You can hear it in their cadence and inflection - it doesn't sound right. (Admittedly, an experienced editor and voice actor might find it easier to spot.)

You can always throw it a loop. Speak a different language, or ask an unexpected question, like, 'What's 3+5?' or, 'Say 'banana.'"

In general, though, you would need a complete set of phonemes in the victim's voice, which you're not going to get simply by calling someone. You'd need them reading something like The Rainbow Passage or Comma Gets a Cure, which generates the proper sounds.