Call up and Join up

Call up verb - Get or try to get into communication (with someone) by telephone.

Join up and call up are semantically related in gather topic. In some cases you can use "Join up" instead a verb "Call up", when it comes to topics like sign up for responsibility, sign up for membership.

Call up and join up are semantically related in gather topic. Sometimes you can use "Call up" instead a verb "Join up", if it concerns topics such as sign up for responsibility, sign up for membership.