Change the sound of voice

I have a wav file. Its a telephone conversation. for training I need to change the sound of one of the voices. Is this an easy thing with Audacity?

The wav file will be played for the company and HR does not want anyone knowing the person on the call…
Thank you,

“Changing” the voice is easy, you can make it sound like a “mud monster” by slowing it down, like a robot with the vocoder effect, like a chipmunk by speeding it up…
Changing the voice so that it sounds natural, but like someone else, no, that is not easy - you’d be better to employ a voice actor or get your brother/sister/uncle/… to speak it.

I tried the effect vocoder and I got an error:

Nyquist did not return audio

See here: http://manual.audacityteam.org/manual/help/manual/man/effect_menu.html#vocoder