The phrase "growing used to" implies acclimation, familiarity or habituation. Antonyms for this phrase, on the other hand, could refer to the opposite of the adjustment process, such as disuse, unfamiliarity, or unaccustomedness. To grow used to something implies a level of comfort and perhaps even enjoyment with the given thing, so antonyms could express dislike, discomfort or even indifference. Disinclination or aversion to something is its antonym. Conversely, an affinity or liking for something is another antonym. In the end, antonyms depend on the context of the phrase "growing used to.