The phrase "get on the line" can be replaced with several synonyms that convey the same meaning. "Get on the phone" is a common replacement for the phrase, as it signifies making or receiving a call. "Get in touch" is also a good alternative, as it can refer to using any method of communication to reach someone. Other synonyms include "make contact," "connect," and "reach out." Each of these phrases can be used in different contexts, depending on the situation at hand. Overall, these synonyms allow for more varied and dynamic language when expressing the act of making contact with someone.