Honda — Honda cb unicorn 150

Address:

Kasaragod, Kerala, 671121

Sir,
i bought my bike on middle 2015.am a resident of kasaragod.at first i got mileage around 50.but few months ago mileage was 32.i showed at honda service center.and changed the parts they said, air filter, spark plug, engine oil and many more.they said now it will get more than 50 milage.but after that also am getting only 40-42 kmpl.its becomming very expensive to me.what should i do?