The phrase "be proxy for" means to act as a substitute or representative for someone or something. Antonyms for this phrase would be to act independently, to be uninvolved, to be unconnected or detached. Other possible antonyms for this phrase could include to act directly, to represent oneself, to work autonomously or to act as an individual. In essence, antonyms for "be proxy for" are words or phrases that describe independence, separation, or direct action, emphasizing that the person or thing is acting without representation or assistance from anyone else.