Hero Motocorp — engine problem

Engine makes heavy sound when we driving more than 59 km than engine parts makes so heavy sound which is abnormal. So please change & give me new bike i purchase the bike in february 2018. This bike have so many problem. Some times self is not work. Large amount of fuel burns just few kilometres. Mileage is also bad. When we purchase the bike dealer say that it's give 74 km/ ltr mileage but it's too low mileage just 40 km/ ltr or too low . It is worst bike