"Gets on the horn" is an idiomatic expression that means to make a phone call. There are many synonyms that can be used interchangeably with this phrase. Some of them include "gives a ring," "makes a call," "dials up," "phones," "places a call," "reaches out," "contacts," "calls up," "rings up," among others. Each of these synonyms has a slightly different connotation, but they all refer to the act of communicating with someone via a telephone connection. So, whether you "give a ring" or "place a call," the important thing is to stay connected with the people who matter in your life.