Kia Motors — Poor average

I have bought kia sonet htx imt turbo 1.0 3 months ago company claimed the average of 18km/L . And I am getting average of 7-8 km/L I want solution of this problem immediately because as 1.5 months I called in the company regarding this problem the company person are saying now that sir it is a turbo engine you will get only this much average.i am very dissatisfied with the average.