Trouble reading nested object property

I am trying to extract a couple of object values from a JSON response containing an array of phone numbers with various attributes. I can extract the phone number, but I am getting the error:

“TypeError: Cannot read property ‘firstName’ of undefined”

I already tried “firstName: data.owner[0].firstName” with the same result.

I want to get to the point of being able to write the output to a file so I can get a CSV output of the numbers and the first/last names.

Any suggestions?