"Call up on" is a phrase that means to request someone or something. The antonyms of this phrase would be to refuse or reject a request. The opposite of calling up on someone would be to ignore them or not ask for their presence or help. Similarly, the antonym of calling up on something would be to disregard or dismiss it. Sometimes, we may also use phrases like "turn down" or "deny" instead of "not calling up on." In conclusion, while "call up on" implies a request, its antonyms suggest a lack of interest or refusal.