What is the difference between ‘call for’ and ‘call upon’?

When you ‘call on’ or ‘call upon’ someone, you pay a visit to the person. Unlike ‘drop in on’, when you ‘call on’ someone, you usually make an appointment. You let the person know in advance that you are coming. Of the two, ‘call upon’ is considered to be formal.

*While he was in Delhi, the former Prime Minister called upon the President.

*Is it okay if we call on your neighbours this evening?

When you ‘call for’ someone or something, you usually shout for the person or thing. This is just one of the meanings of this phrasal verb.

*Maya stood in front of her house and kept calling for her dog.