He can go to the parole officer's supervisor and ask, "May I be assigned to a different parole officer?" The most likely answer will be "No." And his parole officer will learn of it. If he articulates even a slightly valid basis to change officers, his parole officer would have every right to know about and respond to his accusations.
Lots of people don't like their parole officers. Lots of people think their parole officers are too hard on them, make them do too much to prove they're on the straight and narrow, punish them too severely for their violations, etc. But all of that is in a parole officer's job description.

