The phrase "acting for" can be replaced by many different synonyms depending on the context. Some possible alternatives include "representing," "standing in for," "working on behalf of," "speaking on behalf of," "proxying for," "becoming an agent for," "deputizing for," "fulfilling the role of," "holding the position of," and "serving as a substitute for." Each of these options can convey slightly different nuances in meaning, so it's important to choose the synonym that best fits the specific situation in which it's being used. By using synonyms for "acting for," writers and speakers can add variation and complexity to their language.