Hi Carrie!
When I am not answering questions for wonderful people like you, I do actually have a day job. And I have been in this exact same situation before, having to take a call from
Disney's Hollywood Studios.
The absolute best place that I found was located behind
Star Tours - The Adventure Continues (
number 8 on the map of Disney's Hollywood Studios). When you are facing Star Tours, go to the left, and you will find a little cluster of tables and chairs in front of a platform stage, behind the restaurant. The show that was previously held on the stage is not currently running, so this is a really quiet area to stay and talk. It is also tucked out of the way on a dead-end path, so there are not a whole lot of passers-by.
Another place that is pretty quiet is on Sunset Boulevard on the right-hand side, between the "Once Upon a Time" shop and the amphitheater. So just beyond number 44 on the
map of Disney's Hollywood Studios. This is a little side street that is only used as an exit for performances of Beauty & The Beast, which is currently suspended, so it is generally pretty quiet as well, especially the further back on the path you go. There are no tables here so you can either sit on the curb or walk and talk.
I would advise him to avoid holding his call anywhere in Star Wars: Galaxy's Edge or Toy Story Land as they tend to be a little more crowded than the rest of the park.
I hope that this helped, Carrie!
Please come back here if we can help answer any other questions about anything Walt Disney World Resort!
Sarah B.