I was wondering if there was an easy way to do a voice over of a phone call with it actually sounding like someone on the phone instead of just a voice over?
Downsampling it to 8KHz will get you most of the way toward that telephone sound.
Then, to get even closer, use a band pass filter to knock out everything below about 500Hz and above 2000Hz (you can find an example of using Audacity’s equalizer to do this here).
Here’s a demo with the full effect. (Same recording, I didn’t feel like making a second, more-descriptive one. :-) )
(For whatever reason, my copy of Chrome glitches a bit while playing these back. Not sure why. Other programs handle them fine.)