The overwhelming majority of census workers have no office at all; they're part-time workers that are given a laptop computer to go out and do interviews, and then at night they dial-up and transmit their info directly to headquaters. The guy's phone number is likely his home or cellphone number.
All the better.
from the post...
...I called him back at the number provided,...
... he continued to try to contact me. So I called him back again...
she had a phone number.
what does what you said, have to do with what I said?