There are numerous synonyms for the phrase "calling up," which can be used to refer to different types of communication or actions. Some of the most common synonyms include "phoning," "ringing," "dialing," "contacting," "reaching out," "getting in touch," and "reaching someone by phone." Depending on the context, other synonyms may also be appropriate, such as "summoning," "invoking," or "evoking," which could refer to calling up memories or emotions. Additionally, "mobilizing," "rousing," or "enlisting" could be used to describe calling up people to action or duty. Different synonyms for "calling up" can be used to add variety and depth to your writing or speech.