Antibiotics do not reduce your fever
Antibiotics have no direct effect on fever, which is a symptom of disease. Having a fever is a sign that you are ill. You will need antipyretics to fight the fever directly.
Learn more about the diseases that can or cannot be cured by taking antibiotics.
Besides, antibiotics are only useful when you have an illness that is caused by bacteria. The antibiotics will prevent those bacteria from proliferating any further.