The term "changing of heart" is often used to describe a shift in one's beliefs or feelings. Some antonyms for this phrase include steadfastness, inflexibility, and obstinacy. These describe a person who is unwavering in their convictions and unwilling to reconsider their beliefs or opinions. Another antonym for "changing of heart" is indifference, which suggests a lack of emotional investment in a situation or issue. Other antonyms include apathy, callousness, and indifference, which all point to a lack of concern or interest. Overall, these antonyms suggest a resistance to change and an unwillingness to consider new perspectives.