Amazon India — refund wants for havells 3 litre water heater

In Amazon India. Havells 3 litter water heater, I ordered 12th April and I delayed received at 16 th April. When I fix this water heater it works well, after it’s reach the temperature and auto cutoff . After a hour it’s not providing hot water. Then I call Amazon customer care they connect to technician an he said can’t return this product I send a havells technician he will conform about the product.
Next day technician called I didn’t pickup call and he came next day on 19th he checked and said thermal sensor problem I will clear it on Monday 21st. He also not came then call has closed till today nobody came . I don’t want defective product. I want refund of the product and worst service from service centre