Phrasal verbs - usage

call something off		cancel	Pruthvi called the wedding off because he wasn't in love with his fiancé.
call on someone		ask for an answer or opinion	The professor called on me for question 1.
call on someone		visit someone	We called on you last night but you weren't home.
call someone up		phone	Give me your phone number and I will call you up when we are in town.
calm down		relax after being angry	You are still mad. You need to calm down before you drive the car.