Explanation:

- Option 1: Speak to someone over the phone

- This option implies having a conversation with someone using a phone. It is not related to the idiom “call off.”

- Option 2: Visit someone

- This option suggests going to see someone in person. Again, this action does not align with the meaning of the idiom.

- Option 3: Shout someone’s name aloud

- This means loudly calling someone's name, which is different from the idiomatic meaning.

- Option 4: Cancel something

- This is the correct meaning of the idiom "call off." It means to cancel or decide not to go ahead with something planned.