Hyundai Motor India — average issue since purchase date not solve

Address: Hapur court chamber no. 119, Panchsheel Nagar, Uttar Pradesh, 245101

Hello sir
I purchased the i 20 on november 2018.
Registration number is up 37 k 7327
I was facing the mileage problem from the first day when i purchased it.
I visit the hyundai service centre more than 3times but i have still same problem of mileage i also registerd the online complaint to hyundai but the problem but i have still problem of mileage it is only 8-10km per lietre.
The behaviour of staff and customer care service executive is not they did not give me a valuable feedback and the service mechanic didn't resolve my problem.
Sir i requested to you that please resolve my problem as soon as possible
Thank you