prepositions are very important for the meaning of sentences. phrasal verbs depend on prepositions for their meaning. So "Call off" and "call on" have different meanings. Check your knowledge of phrasal verbs
There are about 150 prepositions in English. Yet this is a very small number when you think of the thousands of other words (nouns, verbs etc). prepositions are important words. We use individual prepositions more frequently than other individual words. In fact, the prepositions of, to and in are among the ten most frequent words in English. Many of these prepositions have more than one meaning. Check with a good dictionary for the meanings of these prepositions.