very bad scooter- too problematic

My sister is using a TVS Scooty Pep and she is satisfied with its performance. She suggested me to buy a TVS scooter and I purchased its one of the latest offerings TVS Wego. After few days of usage, I heard a sound coming from the engine as soon as I started the scooter. I showed it to my family and then took it to the service centre of TVS. As the vehicle was in warranty period, they did the repair for free and extended its warranty by 3 months as a nice gesture for the problem caused to their customer. After few months, the problem occurred again and the value of mileage decreased by a noticeable amount. Its mileage dropped from 45 kmpl to 40 kmpl, when asked about the mileage problem, the service mechanics advised me to drive it for more kilometers to increase the mileage. I got annoyed and demanded my money back or I wanted replaced scooter. They did not even consider my request and I am riding this useless Wego.